Problem Solving

I'm not sure how to set up equations for these three problems. I managed to solve two of them through backsolving.

Can you help, pls?

1) If x dollars is invested at 10% for one year and y dollars is invested at 8% for one year, the annual income from the 10% investment will exceed the annual income from the 8% investment by $56. If $2,000 is the total amount invested, how much is invested at 8%?

a. $280
b. $800
c. $892
d. $1,108
e. $1,200

OA is B

2) The time it took car A to travel 400 miles was 2 hours less than the time it took car B to travel the same distance. If car A's average speed was 10 miles per hour greater than that of car B, what was car B's average speed, in miles per hour?

a. 20
b. 30
c. 40
d. 50
e. 80

OA is C

It's obvious that r*t=d should be used here but not knowing rate or time for at least one car slightly confused me.

3) In a sample of college students, 40% are third-year students and 70% are not second-year students. What fraction of those students who are not third-year students are second-year students?

a. 3/4
b. 2/3
c. 4/7
d. 1/2
e. 3/7

OA is D

I tried to set up a grid for this with 3rd year, not 3rd year, 2nd year and not 2nd year entries but perhaps got it wrong.

thanks