You are correct. The answer is choice C.
The other choices A, B, D have each side add up to 180 degrees either because the angles are a linear pair (adjacent and supplementary) or because the angles are same side interior angles. Same side interior angles are supplementary if a transversal line cuts through a pair of parallel lines as so happens in this diagram.
Let
x--------> the amount you have left to spend
y--------> the cost of a shirt you want
z------> the amount of the gift card
we know that
--------> equation 
--------> equation 
--------> equation 
Substitute the equation
and equation
[/tex]

therefore
<u>the answer is the option</u>
x+15 is less than or equal to 60