Javier rode his bike for a total of 40 minutes.
Let x be the minutes Javier ride after lunch
Let y be the minutes Javier ride before lunch
The number of minutes he rode after lunch is 4 times the number of minutes he rode before lunch
x = 4 y
The number of minutes he rode after lunch + number of minutes he rode before lunch = 40
x + y = 40
We know x= 4y
4y + y = 40
5y = 40
y = 8
x= 4y so x= 4(8) = 32
Javier ride 32 minutes after lunch