I need to know what the average speed of the swimmer was

1.5 units^2

Step-by-step explanation:

The average speed of the swimmer=

Total distance/ total time

Total distance = 15+30+45+60

= 150

Total time = 10+20+30+40

= 100

So the average speed will be

150/100

= 1.5 units^2

Another method is that is d is 1.5t

Speed is

1.5t/t

= 1.5

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