Does anyone know how to find the rate with ONLY principal and time? (no interest)

Question

Refer to this:
Investment A: Rate as 'R,' principal as $8000, time as '4 years,' and interest as 'SI'

Answer 1

Nope. There are 4 variables. Knowing only two make it impossible to pin down the other two.

Answer 2

I'll give the full part:

Investment A: Rate as 'R,' principal as $8000, time as '4 years,' and interest as 'SI'
Investment B: Rate as 'R,' principal as $7000, time as '5 years,' and interest as 'SI'

Investment A's Rate and Investment B's Rate is equal to 2:3, and investment B earned more interest than investment A.