You can plot lines by extrapolating two points and connecting them. To extrapolate points on the graph, choose whatever value for x you like, and calculate the correspondent y value.
Line y = x+4:
![\text{choose } x=0 \implies y = 0+4 =4 \implies (0,4) \text{ is on the line}](https://img.qammunity.org/2020/formulas/mathematics/college/jqs8duxlw85955tse4ym440jngzs1sasm3.png)
![\text{choose } x=1 \implies y = 1+4 =5 \implies (1,5) \text{ is on the line}](https://img.qammunity.org/2020/formulas/mathematics/college/7p418bxqxvbqs5ztinu7ghsux0yc9du53j.png)
Line y = -x-6:
![\text{choose } x=-3 \implies y = -(-3)-6 =-3 \implies (-3,-3) \text{ is on the line}](https://img.qammunity.org/2020/formulas/mathematics/college/z9lpgb3w4hwu0c13mrz1d44fhf5y9dzrc8.png)
![\text{choose } x=-6 \implies y = -(-6)-6 =0 \implies (-6,0) \text{ is on the line}](https://img.qammunity.org/2020/formulas/mathematics/college/bejrbogswuslxjjse7o6zz9fpnaor3kkqg.png)
Now draw the first two points (0,4) and (1,5) and connect them. You have the first line. Draw the last two points (-3,-3) and (-6,0) and connect them. You have the second line.
You should find out that the two lines cross at (-5,-1)