Question

12 a number when decreased by 7 gives 45 find the number

Answer 1

let the number be x
x-7=45
x=45+7
x=52
the number is 52

Answer 2

solution is:-

$x - 7 = 45 \\ x = 45 + 7 \\ x = 52$
we don't know the number ,
so we put it x then
we write the equation
then we transfer-7 to RHs thus,
-7 become +7
then we add it with 45 to get the value of x.

check the answer:
we put the value of x in the place x
$x = 52 \\ 52 - 7 = 45$