The sum of Eli's age and Cecil's age is 60. Six years ago, Eli was three times as old as Cecil. Find Eli's age now.

Answer 1

Elis age is = E

Cecils age is = C

So, E+C=60

six yers ago Elis age was E-6 and Cecils age was C-6.

So, applying the condition,

E-6=3(C-6)

>>E-6=3C-18

>> E-6=3(60-E)-18 [putting C=60-E from the first equation]

>> E-6=180-3E-18

>>E+3E=180-18+6

>>4E=168

>>E=168/4

So, E= 42

Elis age is 42

Answer 2

The sum of Eli's age and Cecil's age is 60. Six years ago, Eli was three times as old as Cecil. Find Eli's age now

let x = Eli's age now (note: when practical, pick variable that for answer, so no extra calculation later)

Let y = Cecil's age

x + y = 60

"sum of Eli's age and Cecil's age is 60"

(x-6) = 3*(y-6)

Six years ago, Eli was three times as old as Cecil

x - 6 = 3y - 18

x = 3y - 12

From above, y=60-x. Plug that in:

x = 3*(60-x) - 12

x = 180 - 3x - 12

4x = 168

x = 42

Check (very important)

y = 18

Is 42 + 18 = 60 ??? yes

Is 42 - 6 = 3*(18 -6) ???

36 = 3*12 ??? yes