Solution (not my work):

Probability of coin 1 landing heads up is 1/2. Probability of second coin landing heads up is 1/2.

P(both heads up) = (1/2)(1/2) = 1/4.

Question:

What indicates in the problem that 1/2 is multiplied by 1/2? Taking a test, a student might guess that he or she must add 1/2 to itself.