At a bake sale, David bought 3 tarts and 5 cookies, and paid $10.50. At the same prices, Lisa bought 4 tarts and 8 cookies, and paid $14.80. What was the price of a tart and the price of a cookie?

T = Tarts
C = Cookies

David:
3T + 5C = 10.50

Lisa:
4T + 8C = 14.80

Setup as system of equations and use substitution or elimination

Elimination is easier for this case but either will give you the right answer I worked it both ways

T= cost of tarts = $2.50
C= cost of cookies = $0.60

The answer would be -3.9> -4.5