Question

I thought of a number, added 7 , multiplied by 3 , subtracted 3,divided by 2 , then multiplied by 12,the rest was 72,what was the number i thought of

Answer 1

As a simple method we could just reverse the order and do the inverse each time:
" I thought of a number, added 7 , multiplied by 3 , subtracted 3,divided by 2 , then multiplied by 12,the rest was 72 "

72 ÷12 = 6
6*2 = 12
12+3 = 15
15 ÷ 3 = 5
5-7 = -2

your number was -2

or
(((x+7)*3) - 3)/2*12 = 72
divide by 12

(((x+7)*3) - 3)/2 = 6
multiply by 2
(x+7)*3) - 3 = 12
(x+7)*3 = 15
x+7 = 5
x = -2

in effect I performed the same steps