how to graph the equations 9x+3y=15 and -6x-4y=-8

A common form of a linear equation in the two variables x and y is:

y=mx+b

where m and b designate constants.

In you case:

9x+3y=15

3y=15-9x Diwide wit 3

y=-3x+5

-6x-4y=-8

-4y=-8+6x Divide with -4

y=-(6/4)x+2

y=-(3/2)x+2

y=-1.5*x+2

In google type:
functions graphs online

When you see list of results click on:
rechneronline.de/function-graphs/

When page be open in blue rectacangle type: -3x+5

in gray rectacangle type: -1.5*x+2

and click option Draw

You will see graphs