First find the distance between soccer practice and home by multiplying the distance between soccer practice and school by 2: 12 miles * 2 = <<12*2=24>>24 miles
Then find the total distance Carla drives by adding the length of each trip: 24 miles + 12 miles + 6 miles + 8 miles = <<24+12+6+8=50>>50 miles
Then find how many gallons of gas she needs by dividing the distance of the trip by her car's gas mileage: 50 miles / 25 mpg = <<50/25=2>>2 gallons
Then multiple the gallons of gas by the price per gallon to find the total cost: 2 gallons * $2.50 = $<<2*2.5=5>>5
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