In 2015, there were about 22 million teenagers in the United States.
They each sent an average of 900 text messages per
month.
About how many text messages did all of the teenagers in
the United States send each month?
Express your answer using scientific notation.

in mathematics, a constraint is a condition of an optimization problem that the solution must satisfy. there are several types of constraints—primarily equality constraints, inequality constraints, and integer constraints. the set of candidate solutions that satisfy all constraints is called the feasible set.

hoped i'm right lol

cross multiplying, we get :

⇒ (3) × (5) = (9) × (x)

⇒ 15 = 9x