We have been given that in triangle ABC angle A=45 angle B =40 and a=7. We are asked to find the equation that we can use to solve for 'f'.
We have two angles and opposite sides to these angles.
We will use Law of Sines to solve our given problem.
, where a, b and c are opposite sides corresponding to angles A, B, and C respectively.
The angle opposite to side b is 40 degrees and angle opposite to side a is 45 degrees.
Upon substituting these values in Law of Sines, we will get:

Therefore, our required equation would be
.
Step 1: Distributive Property
Step 2: Subtraction Property of Equality
Step 3: Addition Property of Equality
Step 4: Division Property of Equality
Since it is a parallelogram cente at point T,
then the measure of PT is equal to the measure of TR. And the measure of QT is
equal to the measure of TS.
PT = TR
a + 4 = 2a
4 = 2a -a
a = 4
PT = TR = 8 units
QT = TS
b = 2b -3
3 = 2b – b
b = 3
<span>QT = TS = 3 units</span>