Question

10-10:{1+3*[(39-60:a*2)+21]:10}=9

Answer 1

10-10/[1+3·[39-60/a·2]+21]/10]=9
⇒10/[1+3·[39-60/a·2]+21]/10]=10-9
⇒10/[1+3·[39-60/a·2]+21]/10]=1
⇒1+3·[39-60/a·2]+21]/10]=10/1
⇒1+3·[39-60/a·2]+21]/10]=10
⇒3·[39-60/a·2]+21]/10]=10-1
⇒3·[39-60/a·2]+21]/10]=9
⇒[39-60/a·2]+21]/10]=9/3
⇒[39-60/a·2]+21]/10]=3
⇒[39-60/a·2]+21]=10·3
⇒[39-60/a·2]+21]=30
⇒[39-60/a·2]=30-21
⇒[39-60/a·2]=9
⇒39-60/a·2=9
⇒60/a·2=39-9
⇒60/a·2=30
⇒60/a=30/2
⇒60/a=15
⇒a=60/15
⇒a=4;