Answer :
Answer:
B. 34
[tex]let \: sum \: of \: ages \: of\: 3 \: people \: be \: x \\ 42 = \frac{x}{3} \\ x = 126 \\ let \:age \: of \: fourth \: person \: be \: y \\ 40 = \frac{x + y}{4} \\ 160 = x + y \\ 160 = 126 + y \\ y = 34 \\ = 34 \: years[/tex]