30+30+30=90. How can you make 90 again by using the same number 3 times, but it can’t be 30 ? If a=30 then a+a+a=90 Other formulations using simple infix operators +,−,×,÷ are as follows: If b=91 then b−b÷b=90 If c=90 then c+c−c=90 and c-c+c=90 and c×c÷c=90 and c÷c×c=90 If d=89 then d+d÷d=90 and d÷d+d=90 If e=10 then e×e−e=90 If f=9 then f+f×f=90 and f×f+f=90 If g=3√90≈4.4814 then g×g×g=90 If h=1/90=0.01 then h÷h÷h=90 If j=−9 then j×j−j=90 If k=−10 then k+k×k=90 If l=−89 then l÷l−l=90 If m=−90 then m−m−m=90 If n=1/2±1/2√359i then n−n×n=90