-(r+3)+3(3-5r)=-42

Solution for -(r+3)+3(3-5r)=-42 equation:

Simplifying
-1(r + 3) + 3(3 + -5r) = -42

Reorder the terms:
-1(3 + r) + 3(3 + -5r) = -42
(3 * -1 + r * -1) + 3(3 + -5r) = -42
(-3 + -1r) + 3(3 + -5r) = -42
-3 + -1r + (3 * 3 + -5r * 3) = -42
-3 + -1r + (9 + -15r) = -42

Reorder the terms:
-3 + 9 + -1r + -15r = -42

Combine like terms: -3 + 9 = 6
6 + -1r + -15r = -42

Combine like terms: -1r + -15r = -16r
6 + -16r = -42

Solving
6 + -16r = -42

Solving for variable 'r'.

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

Add '-6' to each side of the equation.
6 + -6 + -16r = -42 + -6

Combine like terms: 6 + -6 = 0
0 + -16r = -42 + -6
-16r = -42 + -6

Combine like terms: -42 + -6 = -48
-16r = -48

Divide each side by '-16'.
r = 3

Simplifying
r = 3