4 pennies = $0.04. 22 coins minus the 4 pennies = 18. So, 18 nickels is equal to $0.90. Because she has at most 22 coins and they're worth at least $0.78 then $0.94 would make since.
This system has no solution. x = -7y + 24 can be rewritten as x = 24 - 7y to simplify x + 7y = 32, we have to subtract 7y from both sides x = 32 - 7y Now, our system is as follows: x = 24 - 7y x = 32 - 7y