Question 313761
p = speed of plane
a = speed of automobile
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p + a = 120

but were gonna make this "a = -p + 120" for the sake of the problem bc that's what works lol.

then the other equation will be 4p + 2a = 400
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4p + 2(-p + 120) = 400

4p - 2p + 240 = 400

2p + 240 = 400

2p = 160

p = 80 mph (plane)

then plug 80 into -p in the other equation...which is a = -p + 120

and that gives you...

a = 40 mph (automobile) 

:) <3