Question 535335
substitute equation (i) to (ii)
4n-5 = 5(n-5)
4n-5 = 5n-25
4n-5n= -25+5
-n   = -20   --> multiply -1
n    = 20
substitute the niece's age to equation(i): u=4n, and we will get that uncle's age was 80, as told.
u = 4n
u = 4(20)
u = 80