Help with the substitution method?

x-y=9
(x-y)+y = 9+y
x= 9+y --Equation 1

4x-3y=31 ---Equation 2
Substitute the value of x that is written in terms of y in equation 1 into equation 2, it follows that
4*(9+y)-3y = 31
4*9+4*y-3y = 31
36+4y-3y = 31
36+y = 31
(36+y)-36 = 31-36
y = -5

Substitute y=-5 into equation 1, then we have
x = 9+(-5)
x = 9-5 = 4

Hence the solution is x=4, y=-5.

4 ( y + 9 ) - 3 y = 31

y + 36 = 31

y = - 5

x + 5 = 9

x = 4

x = 4 , y = - 5

just make one equation x=... or make it y=... then substitute (put wat x or y equals into the other equations) that for (x or y) into the other equation. Should be easy to solve.

solve the first equation for x by adding y to both sides
x-y+y=9+y
x=9+y
substitute this x into the second equation
4(9+y) - 3y= 31
distribute the first term
4*9 + 4y - 3y = 31
simplify
36 +y =31
solve for y by subtracting 36 from both sides
y= -5

now you can substitute y=-5 into the first equation to solve for x
x- (-5) = 9
x+5 = 9
x = 4

solution:: (x,y)=(4,-5)

i'll leave it to you to check that it is correct

x-y=9 (1)
4x-3y=31 (2)

Rearrange (1) to x = y +9 (3)
and substitute into (2)

4 ( y+9) - 3y = 31

4y +36 -3y = 31
y = 31 -36 = -5
Sub. y = -5 into
x = y + 9 = -5 + 9 = 4

Therefore solution is ( 4,-5)

1. Solve the first equation for x in terms of y
x = 9+y

2. Substitute the expression for x into the second equation:
4(9+y) - 3y = 31
36 + 4y - 3y = 31

3. Solve for the value of y
(4-3)y = 31 - 36
y = -5

4. Substitute the value of y into the first equation:
x - (-5) = 9
x + 5 = 9
x = 4

x-y 9
than x=9+y
putting this value of x in 2nd eq
4(9+y)-3y=31
36+4y-3y=31
36+y=31
y= -5
than
x= 9+(-5)
= -4

x-y=9
4x-3y=31
so
x=9+y

Put in x

4(9+y)-3y=31
36+4y-3y=31
36+y=31
y=-5

put in y into the first equation

x-(-5)=9
x+5=9
x=4

x - y = 9
4x - 3y = 31

x - y = 9
x = y + 9

4x - 3y = 31

Substitute y + 9 for x.
4(y + 9) - 3y = 31
4(y) + 4(9) - 3y = 31
4y + 36 - 3y = 31
4y - 3y = 31 - 36
y = -5

x - y = 9

Substitute -5 for y.
x - (-5) = 9
x + 5 = 9
x = 4

∴ x = 4, y = -5