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put this solution on YOUR website!
Let x=number of trips of the larger truck
Then x+18=number of trips of the smaller truck
3(x+18)=amount of freight delivered by the smaller truck
4x=amount of freight delivered by the larger truck
Now we are told that:
3(x+18)=4x+12 get rid of parens (distributive law)
3x+54=4x+12 subtract 4x and also 54 from each side
3x+54-54-4x=4x-4x+12-54 collect like terms
-x=-42 divide both sides by -1
x=42 trips-----------------------number of trips of the larger truck
x+18=42+18=60-------------------------number of trips of the smaller truck
CK
3*60=4*42+12
180=168+12
180=180
Hope this helps---ptaylor