I need help figuring out the question 3 and 5

Suppose your school costs for this term were $4900 and financial aid covered 3/4 of that amount. how much did financial aid cover? and how much do you still have to pay?

The area of a circle is equal to 1 dm². find the radius of the circle.

At your job you're paid $50 per week plus $3 per sale at least how many saled do you need to make in order to have over $250