algebra word problem

Question

At an amusement park you get 5 points for each bull eyes you hit, but you lose 10 points each time you miss. After 30 tries yolansa lost 30 points. How many bull eye did she have.

Answer 1

# Bullseye = B

# Misses = M

B + M = 30

5*B - 10*M = -30

Solve for M in first equation:

M = 30 - B

And substitute for M in second equation to solve for B:

5*B - 10*(30-B) = -30

5*B - 300 + 10*B = -30

15*B = 270

B = 18