-4r-11=4r+21
Move 4r to the other side
Sign changes from +4r to -4r
-4r-4r-11=4r-4r+21
-4r-4r-11=21
-8r-11=21
Move -11 to the other side
Sign changes from -11 to +11
-8r-11+11=21+11
-8r=21+11
-8r=32
Divide both sides by -8
-8r/-8=32/-8
Answer: r=-4
Since the ratio is part-Whole, first you need to find the whole. If you add all of the marble colors together (17+13+23) you get the total marbles (53) in the box. The ratio of red marbles to the total would be 17 to 53.