Answer:
The data that we have is:
For each diamond, you earn 100 points.
If you complete the level in less than 2 minutes, you earn a bonus of 75 points.
You want to earn more than 1575 points.
Now, assuming that you want to write and solve n inequality that represents the numbers d of diamonds you must collect in less than 2 minutes to advance to the next level.
Because you end in less than 2 minutes, then you have the bonus of 75 points.
Then the number of points as a function of d, the number of diamonds, is:
P(d) = 100*d + 75
And you want that:
P(d) > 1575
100*d + 75 > 1575
Now we can solve this for d.
100d > 1575 - 75
100d > 1500
d > 1500/100
d > 15
You must collect more than 15 diamonds.