Answer:





Step-by-step explanation:
Solving (a):
7x - 19 and 3x + 14 are interior angles.
So:

Collect like terms



7x - 19 and 5y - 2 are equal angles --- corresponding angles
So:

Make 5y the subject

5y = 7x -17
Make y the subject

Substitute 



Solving (b):
The triangle is right-angled.
So:

Collect Like Terms



Answer:
x = 5
Step-by-step explanation:
(7x + 16) = 90 - 39
7x + 16 = 51
7x = 51 - 16 = 35
x = 5
Answer:
4
Step-by-step explanation:
4-2
I think that she started with 10.. I'm not 100% sure, though