so 22.5 per barrel
so 22.5
x represents the number of 22.5 barrels
y represents the number of 35 barrels
so
x+y=1250
then find the total cost
1250 barrels
27.5 per so mutiply by 1250 and get 34375 total cost
22.5x+35y=34375
we have 2 senctances
x+y=1250
22.5x+35y=34375
elimination
mulitply first equation by -35 to clear y
-35x-35y=-43750
add to second equation
-35x-35y=-43750
22.5x+35y=34375 +
-12.5x+0y=-9375
-12.5x=-9375
multiply -1
12.5x=9375
divie both sides by 12.5
x=750
subsitute
x+y=1250
750+y=1250
subtract 750
y=500
750 barrells of the 22.5 oil should be included and
500 barrells of the 35 oil should be included