(A) Represent multi-step problems involving the four operations with whole numbers using strip diagrams and equations with a letter standing for the unknown quantity
(Y7) Extend and apply the laws and properties of arithmetic to algebraic terms and expressions (ACMNA177)
6.EE.2 Write, read, and evaluate expressions in which letters stand for numbers.6.EE.3
6.EE.3 Apply the properties of operations to generate equivalent expressions. For example, apply the distributive property to the expression 3 (2 + x) to produce the equivalent expression 6 + 3x; apply the distributive property to the expression 24x + 18y to produce the equivalent expression 6 (4x + 3y); apply properties of operations to y + y + y to produce the equivalent expression 3y.