Freddy wants to become an electrician. He can save $150 a month for three years, and his family has offered to help him with the rest. His training will cost $10,500. How much will his family have to pay?
Freddy will save a total of $150/month x 12 months/year x 3 years = $<<150*12*3=5400>>5400.
So, his family needs to pay $10,500 - $5,400 = $<<10500-5400=5100>>5100. Answer: \boxed{5100}.