The difference between a triple a number and a double a number

Which expression is equivalent to (9x - 3 1/ + 1 3/8)

If point cis between points a and b, then ac + — = ab

Aboat has a speed of 9 mph in calm water. it takes the boat 4 hours to travel upstream but only 2 hours to travel the same distance downstream. which equation can be used to find c, the speed of the current? 2(9 – c) = 4(9 + c) 9 + c = 4(9 – c) 9 – c = 2(9 + c) 4(9 – c) = 2(9 + c)