Question 187894
Let x=son's age; x+5=son's age in 5 years
Then x+20=Mang's age; x+20+5=x+25=Mang's age in 5 years

Now we are told that:
x+25=3(x+5) get rid of parens
x+25=3x+15 subtract x and also 15 from each side
x-x+25-15=3x-x+15-15  collect like terms
10=2x  divide each side by 2
x=5---------------------------------son's present age
x+20=5+20=25-------------------------Mang's present age

CK
5+25=3(5+5)
30=30
 Hope this helps---ptaylor