For the Fist One it’s Pentagonal Pyramid
The answer is 4x + 50.
Step by Step: -25+75= 50
You can’t add or subtract a variable with a number.
The interior angles of a triangle add up to 180 degrees, meaning we can make an equation.



Hope this helps.
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Step-by-step explanation:
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We can Notice that ∠ABC = ∠ACB
We know that if Two Angles are Equal then Angles Corresponding to those Sides are also Equal.
⇒ AB = AC
⇒ 4x + 4 = 6x - 14
⇒ 6x - 4x = 4 + 14
⇒ 2x = 18
⇒ x = 9
⇒ Length of BC = 2x + 7 = 2(9) + 7 = 18 + 7 = 25 units