Helena's sister is 10 years younger than three times her age. The
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Answer:
Step-by-step explanation:
The question is incomplete, as what is required is not stated and the triangle is not given.
So, I will solve generally.
The proof is as follows (see attachment for triangle)
From the attachment, we have:
Make f, e and d the subject
Add up the equations
Collect like terms
We have:
--- angles in a triangle
So, we have:
--- proved
