PSAT math question ?

Question

A school ordered $600 worth of lightbulbs. Some of the lightbulbs cost $1 each and the others cost $2 each. if twice as Many $1 bulbs as $2 bulbs were ordered how Many lightbulbs were ordered altogether?

Answer 1

x is the number of $1 light bulbs

y is the number of $2 light bulbs

x + 2y = 600

2y = x

solve the system by substituting the second equation into the first equation (plug in 2y in the second equation for x in the first equation because x = 2y

2y + 2y = 600

combine like terms

4y = 600

divide both sides by 4

y = 150

because 2y = x, 2*150 = 300 = x

So there are 300 $1 bulbs and 150 $2 bulbs.  

Answer 2

d**n that gave me a headach. the anwser and the question. goddess, don't i know!