a rectangular field has a perimeter of (10a - 6) meters and a width of 2a meters.

Question

what expression represents the length of this field.

Answer 1

P = 2L + 2W

 

Substituting for perimeter and width gives  10a - 6 = 2L + 2(2a).

 

Now solve for the unknown L, in terms of a, by the usual algebra work ("collecting like terms," etc.).