How to find

X-7y=-21

13x-7y=63

y = 4

x = 7

Step-by-step explanation:

First you would rearrange the first equation x-7y=-21 and make x the subject:

x = - 21 + 7y

Then substitute x into the 2nd equation to find y:

13x - 7y = 63

13 (-21+7y) - 7y = 63

-273 + 91y - 7y = 63

-273 + 84y=63

84y = 63 + 273

84y = 336

y = 4

Once you have y you can substitute this into any of the original equations to find x, for example:

x - 7y = - 21

x - 7 (4) = - 21

x - 28 = - 21

x = - 21 + 28

x = 7