Question 1168709

Vinnie drives his car 156 miles and has average of a certain speed. If the average speed had been 5mph more. He could have traveled 168 miles jn the same length of time. What was his average speed?
<pre>Let speed be S
Then we get the following TIME equation: {{{matrix(1,3, 156/S, "=", 168/(S + 5))}}}
168S = 156(S + 5) ------ Cross-multiplying
168S = 156S + 5(156)
168S - 156S = 5(156)
12S = 5(156)
Speed, or {{{highlight_green(matrix(1,6, S, "=", 5(156)/12, "=", 65, mph))}}}