Answer: option d.
Step-by-step explanation:
If <em>y </em>varies directly as <em>x</em> and <em>z</em>, the form of the equation is:
Where<em> k</em> is the constant of variation.
If y=4 when x=6 and z=1 then substitute these values into the expression and solve for <em>k:</em>
<em> </em>Substitute the value of <em>k</em> into the expression. Then, the equation is:
To find the value of <em>y </em>when x=7 and z=4, you must substute these values into the equation. Therefore you obtain:
<em> </em>