Betty saves 3 times as much as Ann. Charles saves 390 less than Ann. If Betty saves 1,330 more than Charles, how much does Charles save

To answer this, I set up a system of equations for each sentence mentioned (B=3A for Betty, A - 390 for Ann, and B = (A - 390) + 1330 to show the relationship between Betty and Charles's amounts. The way to answer this is to replace the B with the 3A that represents Betty's amount. This creates 3A = (A-390) + 1330. By having only one variable you can then solve the equation to find Ann's amount. If you know Ann's amount, you can figure out Charles' amount. To solve the equation add 1330 and - 390 which is the same as subtracting 390 from 1330. This leaves you with 3A = A + 940. Subtract 1A from both sides, to leave you with 2A = 940. Solve for a by dividing both sides by 2. This leaves you with A = 470. Take this value of a and substitute it in to Charles's equation which is C = A - 390. 470 - 390 equals 80. This is Charles' amount saved.