Mary covered her kitchen floor with 10 tiles. the floor measures 6 feet long by 5 feet wide, the tiles are each 3 feet long and w feet wide. write an equation to represent the situation.

Number of tiles used for covering the kitchen floor = 10
Area covered by the floor = 6 * 5 feet^2                                               
                                         = 30 square feet
Length of each tiles = 3 feet
Width of each tiles = w feet
Area covered by each tiles = 3w square feet
Then the equation can be written as
3w * 10 = 30
30w = 30
 w= 30/30     
    = 1 feet
So the width of each tiles is 1 feet. I hope the procedure is clear enough for you to understand. The equation to determine the solution is
10 *3w = 30
There are 10 tiles used and the area covered by each tiles is 3w. Also the area of the floor is 30 square feet. All those information's have been used to get to the equation.

The clear answer is clearly 25 is very clear to me