SOLUTION: solve by the substitution method 3x-9y=69 5x+25=y. the solution

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Question 536435: solve by the substitution method 3x-9y=69 5x+25=y. the solution
Answer by Maths68(1474) About Me  (Show Source):
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3x-9y=69.............(1)
5x%2B25=y..............(2)
Put the value of y in (1)
3x-9%285x%2B25%29=69
3x-45x-225=69
-42x=69%2B225
-42x=294
Divide by -42 both sides
-42%2F-42x=294%2F-42
cross%28-42%29%2Fcross%28-42%29x=-cross%28294%29%2Fcross%2842%29
x=-7
Put the value of x in (1)
3x-9y=69
3%28-7%29-9y=69
-21-9y=69
-9y=69%2B21
-9y=90
Divide by -9 both sides
-9y%2F-9=90%2F-9
cross%28-9%29y%2Fcross%28-9%29=-cross%2890%29%2Fcross%289%29
y=-10
x,y=-7,-10


Check
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Put the values of x and y in (1)
3x-9y=69.............(1)
3%28-7%29-9%28-10%29=69
-21%2B90=69
69=69
Put the values of x and y in (2)
5x%2B25=y..............(2)
5%28-3%29%2B25=-10
-15%2B25=-10
-10=-10