How do you solve the system of equations y = .5x + 20y=.5x+20 and y = .15xy=.15x?

1 Answer
Ken C.
Jul 1, 2016

Use substitution to get a solution of (-400/7,-60/7)(−4007,−607).

Explanation:

We know that y=yy=y, so that must also mean, if y=.5x+20y=.5x+20 and y=.15xy=.15x:
.5x+20=.15x.5x+20=.15x

This is now a linear equation:
.5x+20=.15x.5x+20=.15x
cancel(.5x)+20-cancel(.5x)=.15x-.5x
20=-.35x
x=20/-.35=20/-(35/100)
=cancel20^4*-100/cancel35^7
=-400/7~~-57.14

Since y=.15x:
y=.15*-400/7
=15/cancel100^1*-cancel400^4/7
=-60/7~~-8.57

Thus, the ordered pair that is the solution to this equation is (-400/7,-60/7).

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