Answer :
540 gallons of 90% antifreeze has to be mixed.
Solution:
First, I will set up my table. I will fill in the unknown with variable x.
The table is attached below
From this table, we can easily set up the two equations.
Sum of values of two solutions = Value of mixture
0.9x + 18 = 0.8(x + 90)
0.9x + 18 = 0.8x + 90 x 0.8
0.9x – 0.8x = 72 – 18
0.1x = 54
x = 540
Hence, 540 gallons of 90% antifreeze has to be mixed.
