If 2x+y=5, then y=5-2x, so he substituted 5-2x correctly.
x+4x=5x, so he combined like terms correctly.
If 5x-10=10, then 5x=10+10 -> 5x=20, so he subtracted 10 from the right side instead of adding 10 to the right side.
The answer is C.
Here's the correct solution:
Answer:
x^2 and x
Step-by-step explanation:
<em>HOPE</em><em> </em><em>THIS</em><em> </em><em>WILL</em><em> </em><em>HELP</em><em> </em><em>U</em><em>.</em><em>.</em><em>.</em><em>.</em><em>✌</em><em>✌</em><em>✌</em><em>✌</em>
S = πr(r + √(h² + r²))
400.2 = 3.14(6)(6 + √(h² + 6²))
400.2 = 18.84(6 + √(h² + 36))
18.84 18.84
21¹⁰⁹/₄₇₁ = 6 + √(h² + 36))
- 6 - 6
15¹⁰⁹/₄₇₁ = √(h² + 36)
231²²¹⁰⁰⁵/₂₂₁₈₄₁ = h² + 36
- 36 - 36
195²²¹⁰⁰⁵/₂₂₁₈₄₁ = h²
14 ≈ h
