Set up the problem as follows:
R = the number of hours Ron Worked
number of hours Mary worked = (2R +3) (2R is twice the amount of hours that Ron worked, and add 3 to get 3 more hours, as stated in the problem.)
They worked together a total amount of 57 hours, so an equation can be written as follows:
R + (2R +3) = 57.
Then, solve for R.
First combine like terms to make: 3R + 3 = 57.
Then, subtract 3 from both sides to leave 3R alone on the left side.
3R = 54.
Finally, divide both sides of the equation by 3 to get R.
R = 18.
Therefore, Ron worked 18 hours, and Mary worked:
(2R + 3) = 2 (18) + 3 = 39 hours Mary worked.
Do a quick double check to make sure this makes sense.
Ron's hours + Mary's hours = 57 hours.
18 + 39 = 57. We are correct.