I seriously don’t understand please help

What properties allow transformation to be used as a problem solving tool

y=2x−1 5x−4y=1 is (1,1)(1,1) a solution of the system?

The first week samantha learned to read braille, she could read 10 words per minute. in the second week she increased her speed by 20%. in the third week she increased her speed again by another 25%. how many words could she read per minute by the third week? hurry and tell me!