Answer:
The probability that your team wins
is 9/16, or about
56% of the time.
Complete Solution:
There are many ways to answer the
question:
Make a rectangular diagram with
four rows of the same size. Shade three of the four rows
to represent making the first shot.
Make four columns of the same
size and shade three of them to represent making the second
shot.
There should now be 16 cells in the grid. The 9 cells
that are shaded twice represent success on both shots
which means your team wins without any overtime play.
Since 9 of the 16 equally likely
outcomes reresents wins, the probability of winning is
9/16. 

Complete Solution
(cont.)
A different strategy is to draw
a tree diagram labeled with all outcomes and their probabilities
for each shot. The probability of winning is found by
multiplying the probabilities on the appropriate brances
of the tree.
If
your teammate makes the first shot 3/4 of the time, then
3/4 of those times that she makes the first shot, she
will make the second shot; that is:
(3/4)
×
(3/4) = 9/16
In this case, the probability of winning
without overtime is 9/16.
[Multiplying probabilities here is correct
only if the two shots are independent events. Assume that
they are.] 