Gym a charges a $50 membership fee and $20 per month. Gym b charges a $10 membership fee and $30 per month. After how many months is the total cost the same at both gyms?

4 months.

Making these into an mx + b = y equations, this is my work:

20x+50 = 30x+10

Subtract 20x from each side.

50 = 10x+10

Subtract 10 from each side.

40 = 10x

Divide each side by 4.

x = 4.

You can then input x into each equation and get 130$ after 4 months.