Answer:
360°
Step-by-step explanation:
According to the properties of parallel lines, the following deductions can be made:
<a and <c are exterior angles of same side, therefore they are supplementary.
Thus,
m<a + m<c = 180°
<b and <d, are alternate interior angles, therefore, they are supplementary.
Thus, m<b + m<d = 180°.
The total numbers of degrees of a, b, c, d will all sum up to give 360°.
To solve this we are going to use the unitary circle and the fact that

From our circle we can infer that

and

.
Since

,

We can conclude that 
.
Answer:
The directions for a homemade glass cleaner call for 1 part vinegar to 4 parts water. Mr. Gilbert mixed 2 cups of vinegar with 5 cups of water. Did he use a correct ratio of vinegar to water? Explain.