function tipCalculate (billAmount) {
    let percentage;
    if (billAmount < 50) {
        percentage = .2
    } else if (billAmount >= 50 && billAmount < 200) {
        percentage = .15
    } else {
        percentage = .1
    }
    return percentage * billAmount
}

const bills = [124, 48, 268]
let billPlusTip = [tipCalculate(bills[0]), tipCalculate(bills[1]), tipCalculate(bills[2])]

console.log(billPlusTip)