-1.3(1+1.3r)-7.7r=31.565

Solution for -1.3(1+1.3r)-7.7r=31.565 equation:

Simplifying
-1.3(1 + 1.3r) + -7.7r = 31.565
(1 * -1.3 + 1.3r * -1.3) + -7.7r = 31.565
(-1.3 + -1.69r) + -7.7r = 31.565

Combine like terms: -1.69r + -7.7r = -9.39r
-1.3 + -9.39r = 31.565

Solving
-1.3 + -9.39r = 31.565

Solving for variable 'r'.

Move all terms containing r to the left, all other terms to the right.

Add '1.3' to each side of the equation.
-1.3 + 1.3 + -9.39r = 31.565 + 1.3

Combine like terms: -1.3 + 1.3 = 0.0
0.0 + -9.39r = 31.565 + 1.3
-9.39r = 31.565 + 1.3

Combine like terms: 31.565 + 1.3 = 32.865
-9.39r = 32.865

Divide each side by '-9.39'.
r = -3.5

Simplifying
r = -3.5