ABCD-trapezoid, smaller base-7cm. The middle line of the trapezoid is 3 cm less than the larger base.

ABCD-trapezoid, smaller base-7cm. The middle line of the trapezoid is 3 cm less than the larger base. Find the midline of the trapezoid.

The smaller base is 7 cm. In order to denote a large base, we introduce the variable x. Since the middle line of the trapezoid is equal to the half-sum of the bases, and we know that the middle line of the trapezoid is 3 cm less than the larger base (x – 3), we get the equation:

(7 + x) / 2 = x – 3

7 + x = 2 x – 6

13 = x

x = 13 – large base

13 – 3 = 10 – middle line of the trapezoid