Answer:
Step-by-step explanation:
4.5x=90
x=20 history
28 chemistry
42 math
They add to 90.
History test=x
Chemistry test=1.4x
Math test=(1.5)(1.4)=2.1x
They add to 90
The given in the problem above is an arithmetic sequence with the first term equal to 4 and the common difference is 5. To determine the number of seats on row 23, use the formula, an = a1 + (n - 1) d
Solving for the 23rd term, an = 4 + (22) 5 = 114 seats
Therefore, the answer is there are 114 seats on the 23rd row.
Welcome Bby (;
You find a parallelogram area by this formula:

Where
b is its base and
h, its height.
You get
b's value applying distance between two points formula.
If A and B points form the base:

And
h is the perpendicular distance between both bases.
You can visit next link to know further about it:
https://www.ck12.org/geometry/Distance-Between-Parallel-Lines/lesson/Distance-Between-Parallel-Lines
-GEOM/
And in attached picture you can find an example in progress you may want to finish.