Plug 8 for y
8 = 2x + 4
Subtract 4
4 = 2x
Divide by 2
x = 2
Plug 16 for y
16 = 2x + 4
Subtract by 4
12 = 2x
Divide by 2
x = 6
Substitute 20 for y
20 = 2x + 4
16 = 2x
x = 8
Substitute 22 for y
22 = 2x + 4
18 = 2x
9 = x
So the values are 2, 6, 8, 9
Measure 2 sides, then multiply them, and divide by 2.
I think the answer is 3 but I’m not sure.
Hope this helps!