How to find a missing side of trapezoid prim?

Substitute the information given in the question to the formula for finding the area of a trapezoid (A=.5height (base1+base2)). 171 = (.5) * 18 (10+base2).

Multiply out. 5 by 18: 171 = 9 (10+base 2).

Use the distributive property to multiple out the equation: 171 = 90+9 (base 2).

Use algebra to solve the remainder of the problem. Subtract 90 from both sides: 81=9 (base2), then divide each side by 9. 9=base 2

simple if lines are not parallel then they are inward reversed we look at angles and look at there exterior ie) draw a straight line to it so you cna see how odd they look. if you asked to calculate the length of a missing line we look at opposite sides and either write the opposite same size to its length and opposite same size to its width as a prism as all lines meet. To calculate area we can either separate these into triangles or add more triangles to meet the line you drew to make an angle straight at 90 degree or to make a diagonal to see what two angles are the same in order to process the missing lines position.