x = the number of hot dogs
2.50x - 150 = 300
[You sell each hot dog for $2.50, you spent $150, you want to make $300]
2.50x - 150 = 300 Add 150 on both sides
2.50x = 450 Divide 2.50 on both sides
x = 180
You have to sell 180 hot dogs to make a profit of $300
[proof]
2.50x - 150 = 300
2.50(180) - 150 = 300
450 - 150 = 300
300 = 300
