Numbers and Operations- 2 Digit +/-

Students are expected to:
Add within 100, including adding a two-digit number and a one-digit number, and adding a
two-digit number and a multiple of 10. 

ex:  46+7=           (2 digit by one digit)              Ex: 46+30=           (2 digit and multiple of ten)
 
Given a two-digit number, mentally find 10 more or 10 less than the number, without having to
count; explain the reasoning used.

ex:  50+ 10=                        70-10=

 Subtract multiples of 10 in the range 10-90 from multiples of 10 in the range 10-90.

ex:   84-50=