SOLUTION: PLEASE IM stuck I have the answer from help practice but I dont know how to do the work so I can solve other similar problems 7x-9y=-34 9x+86=y solve by substitution met

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Question 561839: PLEASE IM stuck
I have the answer from help practice but I dont know how to do the work so I can solve other similar problems
7x-9y=-34
9x+86=y
solve by substitution method
the practice walks me through the steps, tells me to use the distributive law (HOW do I do that??) which shows an answer of 7x-81x-774=740 then it says collect like terms (what does that mean??) answer -74x=740 solve for x x=-10
substitute -10 for y in second equation y=-4 solution (-10,-4)
the only part I understand is the last part. Can someone PLEASE walk me through using the distributive law and collecting like term???
Answer by ankor@dixie-net.com(22740) (Show Source):
You can put this solution on YOUR website!
7x - 9y = -34
9x + 86 = y
:
We know y = (9x+86); substitute for y in the 1st equation, and we have
7x - 9(9x+86) - -34
:
distribute the 9 means you multiply both terms inside the brackets by 9, we
7x - 81x - 774 = -34
:
collecting like terms just means add the x's together here:
-74x - 774 = -34
:
Get rid of all the negatives, multiply each term by -1
74x + 774 = 34
:
Subtract 774 from both sides
74x = 34 - 774
74x = -740
divide both sides by 74
x =
x = -10
:
Remember we know that y = 9x + 86
substitute -10 for x
y = 9(-10) + 86
y = -90 + 86
y = -4
:
Our solution, then is x=-10, y=-4
;
:
We can check this in the 1st equation: 7x - 9y = -34
Replace x and y
7(-10) - 9(-4) = - 34
-70 + 36 = -34; remember minus times minus is a plus
-34 = -34; confirms our solutions
:
Are you understanding this a little better now?