What values of x and y satisfy x − 3y = 4 and 2x + y = 7 simultaneously?

We have:

x - 3y = 4

Pass -3y to the second member of equation

x = 4 + 3y

Now replace on the other equation tge value of x

2x + y = 7

2.(4 + 3y) + y = 7

Do the diatributive

2 ×4 + 2×3y + y = 7

8 +6y+y = 7

8 + 7y = 7

7y = 7 - 8

7y = - 1

y = -1/7

Now replace y = -1/7 in any equation

x = 4 + 3y

x = 4 + 3 . -1/7

x = 4 -3/7

x = (4×7 -3)/7

x = 25/7

127 millimeters is the answer