Hi Dimitri,

I would use a letter for each of the weights and write down equations for each of the statements. The equations may be easier to analyze than the english.

Let B be the weight of the boat, T the weight of the trailer and M the weight of the motor.

A boat weighs 1500 lb more than its motor, becomes
B = M + 1500

A boat weighs 1900 lb more than its trailer , becomes
B = T + 1900

Together the boat and motor weigh five times as much as the trailer
B + M = 5 T

The third equation has all three variables in it and the first two have two variables each with B in both of the first two equations. I can subtract 1500 from both sides of the first equation to get

M = B - 1500

Likewise I can subtract 1900 from both sides of the second equation to get

T = B - 1900

Now if I use these last two equation and replace M and T in the third equation I have an equation in B alone. That is

B + M = 5 T, so
B + (B - 1500) = 5 (B - 1900)

Can you now solve this equation for B?

Penny