Answer:
r = 6 3/23
Explanation:
-128+138r=718
add 128 to each side
-128+128+138r=718+128
138r = 846
divide each side by 138
138r/138 = 846/138
r = 846/138
divide top and bottom by 2
r = 423/69
divide top and bottom by 3
r = 141/23
change this to a mixed number
r = 6 3/23