Christine buys 7 hamburgers and 3 sodas for $27.95. Laura buys 5 hamburgers and 4 sodas for $23.40. How much does a hamburger cost?

A. 1.85

B. $3.20

C. $6.80

D. $6.55

E. $3.50

7h+3s=27.95 subtract 7h from both sides

3s=27.95-7h divide both sides by 3

s = (27.95-7h) / 3

Then we are told:

5h+4s=23.4, using s found above makes this equation become:

5h+4 (27.95-7h) / 3=23.4 multiply both sides by 3

15h+4 (27.95-7h=70.2 perform indicated multiplication on left side

15h+111.8-28h=70.2 combine like terms on left side

-13h+111.8=70.2 subtract 111.8 from both sides

-13h=-41.6 divide both sides by - 13

h=$3.20