algebra
posted by Bri on .
please write and equation, show your work, and find the answer:
1.a certain twodigit number has a value that is seven more than six times the sum of its digits. the tens digit is 3 more than the units digit. find the number
2.In Colorado Creek, Darrell can row 24km downstream in 6 hours or he can row 18km upstream in the same amount of time. find the rate he rows in still water and the rate of the current.
3. if the temperature on a Celsius scale is divided by five it is equal to the reading on a Fahrenheit scale. fifteen times the Fahrenheit reading is equal to three times the Celsius reading. please find the temperature on each scale.

2.) distance = time × speed
Let rowing speed in still water be x, current in river be y
Downstream, speed is his natural rowing speed plus the current:
24 = 6(x + y)
Upstream, speed is natural rowing speed minus current:
18 = 6(x  y)
or
4 = x + y
3 = x  y
Add
7 = 2 x
x = 7/2 km/h (and current is 1/2 km/h)
He can row at 3.5 km/h