options: Write, read, and evaluate expressions in which letters stand for numbers.

Identify when two expressions are equivalent (i.e., when the two expressions name the same number regardless of which value is substituted into them). For example, the expressions y + y + y and 3y are equivalent because they name the same number regardless of which number y stands for.

Write and evaluate numerical expressions involving whole-number exponents.

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.
problem_activity: Task
What is the last digit of $7^{2011}$?  Explain.
What are the last  two  digits of $7^{2011}$?  Explain.


correct_option_index: 2