Equal Savings of Alice and Bob

Two friends, Alice and Bob, are comparing their savings. Alice has a savings function represented by the equation:

$$A(t) = 50 + 20t$$

where $$A(t)$$ is the amount of money Alice has after $$t$$ weeks. Bob's savings function is represented by:

$$B(t) = 70 + 15t$$

where $$B(t)$$ is the amount of money Bob has after $$t$$ weeks. After how many weeks will their savings be equal?