Answer:
N+F=42 & F+3N=70 System Solved: Natalie is 14 and Fred is 28
Explanation:
Using variables N=natalies age and F=Freds age
N+F=42 ----> N=42-F (take this and plug it into the other equation)
F+3N=70 so F+3(42-F)=70 [simplify] F+126-3F=70 [further simplify]
-2F=-56 [divide -56 by -2] F=28 [then plug this number into the orig. equation]
So N+28=42 or N=14.