can someone please help me I don't understand and I'm trying to learn this :((

In a parallelogram the two angles on the same side need to equal 180 degrees. So in the picture angle F and angle G need to equal 180:
Add them together:
7x -5 + 3x-15 = 180
Simplify by combining like terms:
10x -20 = 180
Add 20 to both sides:
10x = 200
Divide both sides by 10:
X = 20
Now you know x, replace x in the angle for g and solve:
G= 7x-5 = 7(20) -5 = 140-5 = 135
G = 135 degrees.
In a parallelogram the top and bottom are the same length, so set the two to equal each other and solve for y:
3y = y + 8
Subtract y from both sides:
2y = 8
Divide both sides by 2:
Y = 4
Now replace y and solve for EF:
EF = 3y = 3(4) = 12
EF = 12
Answer:
∠G = 135
EF = 12
Step-by-step explanation:
In parallelogram, adjacent angles are supplementary
∠G + ∠F = 180
7x - 5 + 3x - 15 = 180 {combine like terms}
10x - 20 = 180
10x = 180 + 20
10x = 200
x = 200/10
x = 20
∠G = 7x - 5 = 7*20 -5 = 140 - 5 = 135
In a parallelogram, opposite sides are equal.
EF = GH
3y = y +8
3y - y = 8
2y = 8
y = 8/2
y = 4
EF = 3y = 3*4 = 12