Question 866539
"y varies directly as x" means that {{{y = k*x}}} for some constant k (ie k is a fixed number)



Plug in y = 100 and x=4. Then solve for k



{{{y = k*x}}}



{{{100 = k*4}}}



{{{100/4 = k}}}



{{{25 = k}}}



{{{k=25}}}



So {{{y = k*x}}} gets updated to {{{y = 25x}}}. That is the equation. So we stop here.



Final Answer: {{{y = 25x}}}