a boat wieghs 1500 lb more than its motor and 1900 lb more than its trailer. Together the boat and the moter weight five times as much as the trailer. How much does the boat weigh?
B=1500+M
B=1900+T
B+M=5T
Well, from the first equation
M=B-1500 so put than in the third equation
B+B-1500=5T
2B-1500=5T and now with the second equation
B=1900+T you have two equations.
double that equation, so you have...
2B-1500=5T and the doubled..
2B=3800+2T subtract the first from the second
-1500=5T-3800-2T solve for T. Then, go back and solve for the others.