39/500 needs to be multiplied by 15, which results in 585/500. This is 1.17 as a decimal. 191/200 in diameter needs to be multiplied by 8, which equals 1528/200. This is 7.64 as a decimal.
You can factorize to simplify the expression
The answer would be,

Hope this helped
:D
-3x+13=16
Move +13 to the other side. Sign changes from +13 to -13.
-3x+13-13=16-13
-3x=16-13
-3x=3
Divide by -3 for both sides.
-3/-3x=3/-3
Cross out -3 and -3, divide by -3, then becomes 1*1*x=x
x=-1
Answer: x=-1