Start with the Pythagorean theorem{A²+B²=C², A and B are the sides and C is the Hypotenuse/Longest Side.}
2²+4²=C²
4+16=C²
20=C².....{now square root both sides.√}
√20=√C²
4.472= C
P.S.: hope I helped :)
It's very simple: It's the surface of a base times the height

Step 1: Isolate the absolute value expression.Step2: Set the quantity inside the absolute value notation equal to + and - the quantity on the other side of the equation.Step 3: Solve for the unknown in both equations.Step 4: Check your answer analytically or graphically.
Answer:
C) 21
Step-by-step explanation:
a² + 20² = 29² Use Pythagorean Theorem to solve for a
a² + 400 = 841 Solve for the exponents
- 400 - 400 Subtract 400 from both sides
a² = 441 Take the square root of both sides
a = 21