Algebra Rate Problem

Blake rows his boat against a current 90 yards in 15 mins. With a current, he rows 90 yards in 9 mins. What is the rate at which Blake rows and what is the rate of the current?

Is the rate 8 and the current 1?

say Blake rows with a speed relative to the water V.

The Current has a speed relative to the bank of C.

so you can write 2 equations
=> (V - C) * 15 = 90
and
=> (V+C) * 9 = 90

now rearrange and combine the equations:
V - C = 6
V + C = 10

so substitute one into the other
(6 + C) + C = 10
C = 2,
V = 8.
You almost had it!

D=rt formula. (D: distance, r: rate, t:time)

90 yards = (rate) x (15 minutes)
*divide by 15 on both sides
6 = rate
So the answer = 6 yards per minute.

Same thing for the current:
90 yards = (rate) x (9 minutes)
10 yards = rate
The answer = 10 yards per minute.