Can someone solve number 1? show work !

Area of rectangle = length x width

therefore 

280 feet squared = 7 x 3x + 10
280 = 7(3x+10)
280 = 21x + 30
 
if you take 30 from both sides, then:

250 = 21x

then to find x you divide both sides by 21. 

21x/21 = x, and 250/21 = 11.09 (rounded to 2 decimal places)

therefore x = 11.09.

Then to find the dimensions, we already know that the width = 7 because it is written on the diagram. So we substitute x into the length. 

3x + 10 
=3(11.09) + 10
=33.27 + 10
=43.27.

Therefore, the dimensions are length = 43.27 feet, width = 7 feet