+164 Lucas has 4 fewer one-dollar coins than ten-cent coins. The total value of all the coins $7. How many coins does Lucas have in all?
+318 4 * $1 = $4
$7 + $4 = $11 (Cost of same number of each
type of coins)
$1 + $0.10 = $1.10 (Value of 1 pair)
$11 ÷ $ 1.10 = 10 (pairs)
10 * 2 = 20
20 - 4 = 16
Lucas has 16 coins in all.
+591 $100\cdot(x-4)+10\cdot{x}=100x-400+10x=700$
$110x=1100$
$x=10$
$10+(10-4)=\boxed{16}$
