1) 1.5x + 8 = 3.1x + 16

First, let's simplify the equation by moving all terms with x to one side:

1.5x - 3.1x = 16 - 8
-1.6x = 8
x = 8 / -1.6
x = -5

So, the solution to the equation is x = -5.

2) 2.9x + 7.4 = x + 1.7

Again, let's simplify the equation by moving all terms with x to one side:

2.9x - x = 1.7 - 7.4
1.9x = -5.7
x = -5.7 / 1.9
x = -3

So, the solution to the second equation is x = -3.