cant figure out equation

Question

motor oil is available in three types: regular, synthetic, ad synthetic blend which is a mixture of regular oil with synthetic. bob decides to make 5 qt of his own synthetic blend. how many quarts of regular oil costing $1.20 per quart and how many quarts of synthetic oil costing $3.40 per quart should he mix so that the blend is worth $1.86 per quart?

should only have one variable.

Answer 1

r represents the amount of regular

5 - r represents the amount of synthetic

1.20r + 3.40(5 - r) = 5(1.86)

 

Can you solve for r?

Answer 2

x = quarts of regular

 

5 - x = quarts of synthetic

 

$1.20x + $3.40(5 - x) = 5 ($1.86)

 

Multiply all terms by 100 to eliminate the decimal

 

     120x + 340(5 - x) = 5 (186)

 

  120x + 1700 - 340x = 930

 

                      -220x = -770

 

                            x = 3.5 quarts

 

3.5 quarts of regular and 1.5 quarts of synthetic