Question

If 3x + y = 18, then 2(3x +y) =__________

Answer 1

treat "3x + y" as one variable, for example v
if v = 18, 2v will be twice that, right?
therefore, 2(3x+y) = 36

if x is 5, then 2x + 5 = 2(5) + 5 = 15
15 - x = 15 - 5, so 2x + 5 is 10 more than x

same principle on 3 as 1, only you're using the distribution property as well... 3x + 3y = 3(x+y)
therefore, 3x + 3y = 36 (which is 3*12, since x+y = 12)

3.6 + 6.4 = 10
x + y = 10
100*(x+y) = 100*10, = 1000