This is the problem that I am having trouble with for my test review. I am completely blank and don't know what it is asking for. Can you please guide me step by step. For example: Why did constant k appear all of a sudden? Thanks in advance I can't post images so here is the link
"$a$ varies directly with $b$" basically says "if you double $b$, then $a$ is doubled; if you multiply $b$ by $10$, then $a$ gets multiplied by $10$", etc.; the two are in direct proportion to each other. The constant $k$ is the proportionality factor. For instance, if the values $1,2,3,4$ for $b$ correspond to values $2,4,6,8$ for $a$, then the proportionality constant is $k=2$, whereas if the values $1,2,3,4$ for $b$ correspond to values $5,10,15,20$ for $a$, then the proportionality constant is $k=5$. I suggest that you play around with the equations offered as choices on the right and convince yourself that the last one is the only one that has the above property. The explanation on the lower left explains that in terms of formulas.