Explanation:
we can do all the things we did with equations (equalities) also with inequalities.
the only exception : when multiplying by a negative number the inequality sign flips direction.
4v + 4 >= 20 | divide both sides by 4
v + 1 >= 5
v >= 4
2v - 1 >= -7
2v >= -6
v >= -3
so, the interval for v that satisfies both inequalities is
[4, infinity)
because starting with 4 (and then any number larger than 4) this is also valid for the second inequality.
but any value between -3 and +4 is invalid for the first inequality.
please not that I used the round bracket for the infinity side, because infinity is not a value that can be reached. so, it cannot be included in the interval.