Answer:
43
Step-by-step explanation:
You will have to use the PEMDAS rule here. so Parntheses goes first, then exponents, then mutiplicaton or division, and finally addition or subtraction.
20-7= 13
-2^2 = (-2 * -2) = 4
9/3 = 3
so... 13*3 = 39+4 =43
pythagorean theorem. a^2+b^2=c^2
1.5^2+b^2=6^2
2.25+b^2=12
12-2.25=b^2
b^2=9.75
take the square root
b=3.12
