What is a=4 and b=2, then 3a + 3b equals to?

This is a substitution problem.  Substitute the known value for "a" and "b" into the equation and solve:

Thus, the equation becomes  3(4) + 3(2) = 12 + 6 = 18

or by the distributive law  3(4) + 3(2) = 3(4 + 2) = 3(6) = 18

18 I think

3x4=12
3x2=6
12+6=18

It is equal to 18 .

3a+3b=3*4+3*2
        =12+6
        =18