Which situation results in a final value of zero

Which expression demonstrates the use of the commutative property of addition in the first step of simplifying the expression (-1+i)+(21+5i)+0

Type the correct answer in each box. use numerals instead of words. if necessary, use / fir the fraction bar(s). the graph represents the piecewise function: h

Two years ago a man was six times as old as his daughter. in 18 years he will be twice as old as his daughter. determine their present ages.