We have been given that Sterre charges $35 to file tax returns, but files for free if she only needs the easiest form. Also, she donates $2 to clean water projects per tax return she files.
Further we know that Sterre charged $7,245 and made a donation of $1,242 this year for the tax returns she filed.
Let x be the number of free income tax returns and y be the number of $35 income tax returns.
Therefore, we can set up:

Since she donates $2 for each return that she files, therefore, we can set up:

Therefore,
Sterre filed 414 tax returns for free and filed 207 tax returns for $35.
ANSWER. BBB
Step-by-step explanation:
Recall that:
sin(A + B) = sinAcosB + cosAsinB
Therefore:
sin11°cos19° + cos11°sin19° = sin(11° + 19°)
= sin30° = 0.5
I hope this explains it.
It's A. Segments that intersect at the right angle