Answer:
For problem #3, we are given
so we would just subtract 7 from both sides to get rid of the 7 on the left and that would end up subtracting 7 from 20 also leaving us with
.
For problem #4, we are given
so we would just divide both sides by 2.1 which would get rid of the 2.1 on the left and that would also make us divide 23.1 by 2.1 leaving us with
.
Hope this helps! Let me know if you have any questions