what number must be added to 3 and 8 so that the ratio of the first number to the second number is equal to 3 :4​

what number must be added to 3 and 8 so that the ratio of the first number to the second number is equal to 3 4 class=

Respuesta :

The answer is 12.
Steps
If that number is x
(3+x)/(8+x)=3/4
"Cross multply"
4(3+x)=3(8+x)
12+4x=24+3x
x=12
To check: add 12 to 3 and 8. 3+12=15 and 8+12=20. 15/20=3/4