Respuesta :

If 15 is 3/8 of x(our number we are trying to find), the we can set up the equation:
15 = x * 3/8
15 * 8 = x * 3 (multiplied both sides by 8)
120 = 3x
120 / 3 = x (divided both sides by 3)
40 = x 

Therefore, 15 is 3/8 of 40. 
How i do it is 15/3=5 then 5 multiplied by 8 which gives you 40 ( quicker answer )