SOLUTION: Two numbers have a sum of twenty. If the second is five less than four times the first, what are the. two numbers?

Question 455280: Two numbers have a sum of twenty. If the second is five less than four times the first, what are the. two numbers?
Answer by mathmartian(7) (Show Source): You can put this solution on YOUR website!
First, define your variables.
x=first number
y=second number
Now write algebraic equations.
Two numbers have a sum of twenty, or x+y=20
The second is five less than four times the first
is =
five less than -5
four times x4
y=4x-5
Now you have a system of equations to solve. Since the second equation has y isolated, it is simple to use the substitution method.
Substitute y=4x-5 for y in the first equation, x+y=20
x+(4x-5)=20
5x-5=20 Collect like terms
5x=25 Add 5 to both sides
x=5 Divide both sides by 5
To solve for y, substitute x=5 into any of the two equations and solve for y.
y=4x-5
y=4(5)-5
y=20-5
y=15
So the two numbers are 5 and 15 :)

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