standard_description: Subtract multiples of 10 in the range 10-90 from multiples of 10 in the range 10-90 (positive or zero differences), using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used.
problem_activity: Two expressions are given below.
Expression A:
$${5q-r}$$
Expression B:
$${ -2q+3r-4}$$
a.   Write a simplified expression that represents A + B.
b.   Write a simplified expression that represents A - B.


aligns: no