A car and a bus start from two places and run opposite each other. The speed of the car is 100 km/h, and the speed of the bus is 80 km/h. After b hours, the two cars meet. What is the length of the road between A and B? ． (Fill in the formula with letters)
轿车和客车从两地出发，相对而行，轿车的速度是100千米/时，客车速度是80千米/时，b小时后两车相遇，甲、乙两地间的公路长多少千米．(填含有字母的式子)
<gadget id="calculator">100 + 80</gadget>
<output>180</output>

<result>180</result>