How to use "when" in Japanese
(I am referring to the Genki series book)
How would you say:
"I often ate hamburgers when I was a child."
and
"Takeshi did not study much when he was in highschool."
I notice that the word "toki" is used for when, but I'm a little confused.

Question

How to use "when" in Japanese
(I am referring to the Genki series book)  
How would you say:
"I often ate hamburgers when I was a child." 
and
"Takeshi did not study much when he was in highschool."
I notice that the word "toki" is used for when, but I'm a little confused.

Answer

"I often ate hamburgers when I was a child." 
Watashi ga kodomo no toki yoku hamberger wo tabeta

"Takeshi did not study much when he was in high school."
Takeshi ga chugakko no toki amari benkyo shinakatta