I need help learning to solve substitution.

Question

I have a problem that says

solve the system by substitution
-4.5x-2y=-12.5
3.25x-y=-0.75

Answer 1

substitution means solving for one variable in terms of another , then substituting the solution into a separate equation

in the 2nd equation
... adding y ... 3.25x = y - 0.75
... adding 0.75 ... 3.25x + 0.75 = y

now substitute the value of y into the 1st equation

-4.5x - 2(3.25x + 0.75) = -12.5

distributing ... -4.5x - 6.5x - 1.5 = -12.5

collecting like terms ... -11x - 1.5 = -12.5

adding 1.5 ... -11x = -11

dividing by -11 ... x = 1

substitute the value of x into a previous equation to find the value of y

Answer 2

Look over your equations and see if any contain a single x or y, that makes it easier.

in your case, the second:
3.25x-y=-0.75
-y = -.75 - 3.25x
y = .75 + 3.25x

-4.5x-2y=-12.5
I would clean it up by multiplying each term by -2
9x + 4y = 25
now sub the first part into this equation.

9x + 4(.75 + 3.25x) = 25
9x + 3 + 13x = 25
22x = 22
x = 1

plug that back into y = .75 + 3.25x
y = .75 + 3.25(1) = 4

so x=1 and y = 4
OR
we have the ordered pair (1,4)