I do khan academy 2 but sorry the answer
The area of ABC is ...
... area = (1/2)(BE)(AC) = (1/2)·3·4 = 6
The triangles ABC and ADC are congruent, so ...
... the area of ∆ADC is 6 square units.
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A reflected image is congruent with its pre-image.
x = 10
-0.80 = 0.13x - 0.21x
-0.80 = -0.08x
-0.80/ -0.08 = -0.08 x / -0.08
x = 10
If we convert these numbers into decimals, then
-0.80 * 100% = -80%
-0.08 * 100% = -8%
-80% ÷ -8% = 10 the negative signs cancel each other.
I'd say a good problem would be 5n+10d=125