$1.$ Over the past three years, you earned $$15$K$,$ $$25$K$,$ and $$17$k$.$ What was your average income?

$2.$ Over the past three years, you earned $15\%,-25\%,$ and $5\%$ interest. What was your average interest?

$3.$ Your portfolio consists in stock of equal shares in three companies with a price to earnings $($P$/$E$)$ ratio of $5,10,$ and $15.$ What is the average P$/$E of your portfolio? Please answer each question with an explanation. The answers are $1.19$K $2.-3\%,3.8\mathrm{.}18)$ in order. Thanks!