Question

Alex thinks of a number. he adds 18 then divides it by 2. he gets the same answer that he would have if he had multiplied the original number by 5. calculate the mystery number.

Answer 1

Alex thinks of a number

x

he adds 18 then divides it by 2

+ 18 ÷ 2

he gets the same answer

=

if he had multiplied the original number by 5

x × 5

Put them all together

x + 18 ÷ 2 = x × 5
x + 18/2 = 5x
x + 9 = 5x
9 = 5x - x
9 = 4x
9/4 = x