Sam bought a total of 25 hamburgers and hot dogs. his total bill was $70.50. if each hamburger cost $3 and each hot dog cost $2.50, how many hot dogs did sam buy?

$3-$2.50=$0.50 (difference in $ of each hot dog and hamburger)

take 25 total as all hamburgers
25x $2.50=$62.50
$70.50-$62.50=$8
$8 ÷ $0.50 = 16

16 hot dogs, 9 hamburgers

Check :
16 x $3 = $48
9 × $2.50 = $22.50

$48+$22.50=$70.50