Expensive 5040

The auto parts store received a shipment of 30 pieces of motor oil for €396. More expensive oil costs €15, cheaper €12. How many amounts of more expensive and cheaper oil were in the shipment?

Correct answer:

a =  12
b =  18

Step-by-step explanation:


a+b=30
15a+12b = 396

a+b=30
15·a+12·b = 396

a+b = 30
15a+12b = 396

Pivot: Row 1 ↔ Row 2
15a+12b = 396
a+b = 30

Row 2 - 1/15 · Row 1 → Row 2
15a+12b = 396
0.2b = 3.6


b = 3.6/0.2 = 18
a = 396-12b/15 = 396-12 · 18/15 = 12

a = 12
b = 18

Our linear equations calculator calculates it.



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