Find the missing variable for a tralezoid. a=68^2 b=
h=4 b=21

The answer is:  " 2291 units " .

Explanation:

Formula for "Area of a trapezoid" :

Area = (1/2) * (base length 1 + base length 2) * height;

or:  A = (1/2) * (b + B) * h.

We are missing the value for "b" one of the base lengths.

However, since:  A = 68² (given) ;  B (the other base length) = 21;  and the perpendicular height, "h" = 4 ;  we can plug this values into the formula, and solve for "b" ;

A = (1/2) * (b + B) * h ;  ↔  68² = (1/2) * (b + 21) * 4 ;

 ↔  4624 = 2 (b + 21) = 2b + 42 ;

 ↔  4624 = 2b + 42 ; 

 ↔  2b + 42 = 4624 ;

Subtract "42" from each side of the equation:

     2b + 42 - 42 = 4624 - 42 ;

to get:   2b = 4582 ;

    Now, divide each side of the equation by: "2" ; to isolate "b" on one side of the equation; and to solve for "b" ;

             2b / 2 = 4582 / 2 ;

 to get:    b = 2291 units.