Answer :
First you add 11 to both sides
6a-11=13
+11 +11
So you get:
6a=24
Next divide both sides by 6
6a=24
6 6
A=4
6a-11=13
+11 +11
So you get:
6a=24
Next divide both sides by 6
6a=24
6 6
A=4