Makakuha ng mga sagot mula sa komunidad at mga eksperto sa IDNStudy.com. Hanapin ang mga solusyong kailangan mo nang mabilis at madali sa tulong ng aming mga eksperto.

Seven years ago, Davy was six times as old as Christine. One year from now, he will only be twice as old. How old are Davy and Christine?

Sagot :

Let Davy's present age be D and Christine's be:
We know that:
[tex]D-7=6(C-7) \\ D-7=6C-42 \\ D=6C-35[/tex]
and 
[tex]D+1=2(C+1) \\ D+1=2C+2 \\ D=2C+1 [/tex]

So 2C+1 is equal 6C-35
[tex]2C+1=6C-35 \\ 36=4C \\ 9=C[/tex]

Therefore Christine is 9 and Davy is (2*9)+1=19 years old