How do i solve e=mcsquared solving for c

One card is dealt from a 52 card deck. find the probability that the dealt card is a 4 or a black 7

Grading scale 1 has the following weights- (tests- 50% quiz- 25% homework- 15% final exam- 10%). calculate your final average if your performance in the class is as follows-test grades- {88, 84, 90, 75, 70, 81); quiz grades- {88, 67, 90, 90, 45, 99, 76, 98, 100}; homework- 90; final exam- 75

What is the definition of a surd. give an example.