What part of math do we actually need in the future

Jose predicted that he would sell 48 umbrellas. he actually sold 72 umbrellas. what are the values of a and b in the table below? round to the nearest tenth if necessary

Use sigma notation to represent the following series for 9 terms.

Rewrite the expression in z to the n power. the expression i was given is: 1 over z to the negative 1 half power.