Ok so you have to replace all x by 4:
F(4)= 4.4+7= 23
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Assuming you are asking what does x represent when you say "What does represent" the answer is a: the number of days it take the brothers to paint 13 pictures.
The first 2 sentences are useless and don't tell you anything (well they do but you don't need the information).
Both brothers can paint 13 pictures in x days.
So x means days, more specifically, the number of days it took for the brothers to paint 13 pictures.
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The common meaning of area<span> restricts it to nonnegative </span>numbers<span>.</span>
Part A: Yes, Triangle DEF and DBC are the same triangle, but DBC is smaller than DEF because it is just a cut off of DEF.
Part B: I am pretty sure it is angle C.
Part C: I am pretty sure it is angle D.
