Brian has reduced his cholesterol level by 18% after his last check up. If his original level was 220, what is his approximate
cholesterol level now?
A. 260
B. 180
OC. 40
D. 216

B

Step-by-step explanation:

multiply 18% and 220 which is 39.6

subtract 39.6 from 220 which is 180.4

simplify

the solution of the equation is 2.23 ⇒ answer b

step-by-step explanation:

* lets revise the meaning of exponential function

- the form of the exponential function is y = ab^x, where a ≠ 0, b > 0 ,  

  b ≠ 1, and x is any real number

- it has a constant base b

- it has a variable exponent x

- to solve an exponential equation, take the log or ln of both sides,  

  and solve for the variable

* lets solve the problem

∵

- the base is 7 and the exponent is x

- insert ㏑ in both sides

∴

- use the rule

∴ x ㏑(7) = ㏑(77)

- to find x divide both sides by ㏑(7)

∴

* the solution of the equation is 2.23 to the nearest 2 decimal places

they would have to work 32 hours.