Question 124497
Let x=son's present age; x+10=son's age in 10 years
Then x+27=Mr. Lee's present age; x+37=Mr. Lee's age in 10 years

Now we are told the following:

x+37=2(x+10) get rid of parens

x+37=2x+20  subtract 20 and also x from each side
x-x+37-20=2x-x+20-20  collect like terms

17=x or
x=17---------------------son's present age
x+27=17+27=44----------------Mr. Lee's present age

CK
44-17=27
27=27
also
44+10=2*27
54=54

Hope this helps----ptaylor