Does anyone know how to do this? me

On the x column, you would write 1, 2, 3, 4, and so on. Then, in the y box, you plug in that number into the equation. Write your answer in the y column. 

For example, if x = 1, then 1^2 + 2 - 8 = - 5. 
If x = 1, y= -5

Since we have 7 spaces lets use 1,2,3,4,5,6, and 7 for x:

y=1^2+2x-8
y=1+2-8
y=-5

y=2^2+4-8
y=8-8
y=0

y=3^2+6-8
y=15-8
y=7

y=4^2+8-8
y=16

y=5^2+10-8
y=27

y=6^2+12-8
y=40

y=7^2+14-8
y=49+14-8
y=49+6
y=55

The completed chart:
x | y
1 | -5
2 | 0
3 | 7
4 | 16
5 | 27
6 | 40
7 | 55

21 is the answer the answer is 21