Joe is 5 years older than Sydney. The sum of their ages is 45. What is Sydney’s age?

20 years old

Step-by-step explanation:

Joe = J

Sydney = S

J = 5 + S

J + S = 45

Substitute

5 + S + S = 45

Add

5 + 2S = 45

Subtract 5 from both sides of the equation

2S = 40

Divide both sides of the equation by 2

S = 20

Sydney is 20 years old

Hope this helps :)

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