Question

Mo-Qui has studied Spanish for half an hour longer than he studied History.

Answer 1

So,

Let s represent the time Mo-Qui spent studying Spanish and h represent the time Mo-Qui spent studying History.

s = h + 30
s > 2 hrs. 15 mins. (he isn't done yet)

Substitute
2 hrs. 15 mins. = h + 30 mins.

Subtract 30 mins. from both sides
1 hr. 45 mins. = h

However, s > 2 hrs. 15 mins., so h must be more than 1 hr. and 45 mins.

h > 1 hr. 45 mins.

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