Which of the summation properties or formulas require the lower index to be 1? Check all that apply.

How many solutions does the nonlinear system of equations graphed bellow have?

Two times a number plus three times another number equals 4. three times the first number plus four times the other number is 7. find the numbers

Koji is installing a rectangular window in an office building. the window is 823 feet wide and 534 feet high. the formula for the area of a rectangle is a=bh. what is the area of the window? enter your answer as a mixed number in simplest form in the box. $$ ft2