4. An item is priced at 80 yuan. If you buy one such item and pay with 10 yuan, 20 yuan, and 50 yuan denominations, there are $\qquad$ different ways to pay.
【Analysis】There are 7 ways.
$$
\begin{aligned}
80 & =8 \times 10 \\
& =6 \times 10+1 \times 20 \\
& =4 \times 10+2 \times 20 \\
& =2 \times 10+3 \times 20 \\
& =4 \times 20 \\
& =3 \times 10+1 \times 50 \\
& =1 \times 10+1 \times 20+1 \times 50
\end{aligned}
$$