if 3x+7=10-2y what is the value of 6x+4y

Add 2y to both sides; subtract 7 from both sides; double each term in the  resulting equation.

6 is da answer

If we add 2y to both sides, we get 3x+2y=10-7, 3x+2y=3. Since we are finding for 6x+4y, double both sides of the equation, so  6.