If y varies directly with x and y is 10 when x is 5 then what is y when x is 2

y is 4

Step-by-step explanation:

so the equation is y = kx ( k is the constant)

We've been given x as 5 & y as 10 so we can use these values to find the constant .

10 = k(5)

k = 2

so now , we can find y

y = 2 × 2

y = 4

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

the answer would be 0.54