數學問題(help!)

Let the no. of hours Simon spend on studying be x

The no. of hours John spend on studying = 3x

This week Simon spent (x + 6) hours and John spent (3x + 6) hours

(3x +6 ) - (x+6) = 12

3x +6 - x -6 = 12
2x = 12
x = 6


Ans. Normally John spends 18 hours and Simon spends 6 hours on studying in a week.

Let John normally spend x hours on studting in a week.
Let Simon normally spend y hours on studting in a week.

The number of hours John spends on studying is normally three times that of Simon

x = 3y----------(1)

This week ,each of them spends 6 hours more on studying . As a result , John spends 12 hours more than Simon

x+6 = (y+6) + 12-------(2)

From (2),

x+ 6 = y + 6 + 12
x = y + 12

Since x = 3y,

x = y + 12
3y = y + 12
2y = 12
y = 6
x = 3y = 3 * 6 = 18.

John normally spend 18 hours on studting in a week.
Simon normally spend 6 hours on studting in a week.