y, is the simple moving average of 5 periods, starting at t4.
r, is calculated with previous 5 periods.
t0: x0=1, y0=(1)/1
t1: x1=2, y1=(1+2)/2
t2: x2=3, y2=(1+2+3)/3
t3: x3=4, y3=(1+2+3+4)/4
t4: x4=5, y4=(1+2+3+4+5)/5 ,r4=1
t5: x5=7, y5=(2+3+4+5+7)/5 ,r5= 0.9974
t6: x6=6, y6=(3+4+5+7+6)/5 ,r6=0.8826
t7: x7=8, y7=(4+5+7+6+8)/5 ,r7= 0.906
t8: x8=9, y8=(5+7+6+8+9)/5 ,r8= 0.917

Q: t9: x9=?, y9=(7+6+8+9+x9)/5, r9=0.9
How do I get x9 (nearest to  x8) for r9=0.9.