Answer:
7.19%
Step-by-step explanation:
let i be the effective rate

This in what I got:
(-7i)(10i)
-70i
To figure this out, replace the variables with their given values.
p(a/b) = p(.4/.5)
Then you divide!
.4/.5 = .8
Hope this helps!
X/3 - 38 = 42
x/3 = 80
x = 240