Cross Multiplication

(C) Model and solve one-variable equations with variables on both sides of the equal sign that represent mathematical and real-world problems using rational number coefficients and constants

(Y10) Solve linear equations involving simple algebraic fractions (ACMNA240)

7.RP.2 Recognize and represent proportional relationships between quantities.

7.RP.2.C Represent proportional relationships by equations. For example, if total cost t is proportional to the number n of items purchased at a constant price p, the relationship between the total cost and the number of items can be expressed as t = pn.

HSA.REI.2 Solve simple rational and radical equations in one variable, and give examples showing how extraneous solutions may arise.