The number of conversion periods, if the interest on a principal is compounded every two months is _____.

A student can type $21$ pages in $15$ minutes. At the same rate, how many minutes will it take the student to type $84$ pages? (Write the answer without unit)

If $35$ women can do a piece of work in $16$ days, in how many days will $28$ women do the same work?

When$x=5 \text{ and} y=5$find $k$ if $x$ and $y$ vary directly

When$x \text{and} y$ vary inversely find the constant of variation when $x=64 \text{and} y=0.75$