Answer:
It is the branch of math that is in charge of dealing with letters known as variables.
Step-by-step explanation:
These variables are used to fill in the place of missing numbers in an equation or solution.Algebra is widely used all over the world in schools.
1,800??
20 Answer: a₁ = 4
<u>Step-by-step explanation:</u>
21 Answer: n = 13
22 Answer: n = 5
42