2a. true
2b. false
2c. true
2d. false
2e. true
2f. false
2g. false
2h. true
2i. true
4.
line 5: if statement should use () parentheses, not {} brackets
line 5: = should be ==
line 5: smaller is out of scope here
line 10: void should be int
line 13: => should be >= (or better yet, no if test is needed)
line 16: should not write variable's type of int when returning it
line 16: int smaller is out of scope here (declare outside if or return directly)
6a. 13 21
6b. 5 6
6c. 6 5
6d. 7 11
8. The program's brace placement makes it so if number % 3 == 0 the number isn't odd, if I had number as 9 then it wouldn't read 9 as odd. The else statement is nested with the closest if statement so to fix it you have to do the following
if (number % 2 == 0) {
    if (number % 3 == 0) {
        System.out.println("Divisible by 6.");
    }
} else {
    System.out.println("Odd.");
}
10.
a = 2;
if (x < 30) {
    x++;
}
System.out.println("Java is awesome! " + x);
12.import java.util.*;
public class Bills {
    public static void main(String[] args) {
        Scanner pikachu = new Scanner(System.in);
        int Bills1 = Bills(pikachu, "John");
        int Bills2 = Bills(pikachu, "Jane");
        System.out.println("John needs " + Bills1 + " bills");
        System.out.println("Jane needs " + Bills2 + " bills");
    }

    public static int Bills(Scanner console, String name) {
        System.out.print("How much will " + name + " be spending? ");
        double amount = pikachu.nextDouble();
        System.out.println();
        int numBills = (int) (amount / 20.0);
        if (numBills * 20.0 < amount) {
            numBills++;
        }
        return numBills;
    }
}
14.
Scanner pikachu = new Scanner(System.in);
System.out.print("Enter a card: ");
String rank = pikachu.next();
String suit = pikachu.next();
if (rank.equals("2")) {
    rank = "Two";
} else if (rank.equals("3")) {
    rank = "Three";
} else if (rank.equals("4")) {
    rank = "Four";
} else if (rank.equals("5")) {
    rank = "Five";
} else if (rank.equals("6")) {
    rank = "Six";
} else if (rank.equals("7")) {
    rank = "Seven";
} else if (rank.equals("8")) {
    rank = "Eight";
} else if (rank.equals("9")) {
    rank = "Nine";
} else if (rank.equals("10")) {
    rank = "Ten";
} else if (rank.equals("J")) {
    rank = "Jack";
} else if (rank.equals("Q")) {
    rank = "Queen";
} else if (rank.equals("K")) {
    rank = "King";
} else { // rank.equals("A")
    rank = "Ace";
}

if (suit.equals("C")) {
    suit = "Clubs";
} else if (suit.equals("D")) {
    suit = "Diamonds";
} else if (suit.equals("H")) {
    suit = "Hearts";
} else { // suit.equals("S")
    suit = "Spades";
}

System.out.println(rank + " of " + suit);
16.
public static int countFactors(int n) {
    int count = 0;
    for (int i = 1; i <= n; i++) {
        if (n % i == 0) {
            count++;
        }
    }
    return count;
}
18.6.800000000000001 roundoff error