Pl help I have to find what the letter is equal to

1. C divided by4=5
C=

2. 9d=27
D=

3. 2a+9=17
A=

4. 4b-12=24
B=

5. True or false
K is 6,are the following equations true or false

1. Kx8=54
2. 9+k=2k+3

Guys plsss urgent

You can find the constant of proportionality by finding the ratio of

Prove (a) cosh2(x) − sinh2(x) = 1 and (b) 1 − tanh 2(x) = sech 2(x). solution (a) cosh2(x) − sinh2(x) = ex + e−x 2 2 − 2 = e2x + 2 + e−2x 4 − = 4 = . (b) we start with the identity proved in part (a): cosh2(x) − sinh2(x) = 1. if we divide both sides by cosh2(x), we get 1 − sinh2(x) cosh2(x) = 1 or 1 − tanh 2(x) = .

What is the total area of the figure?