If $a$ and $b$ are constants and the equation

has infinitely many solutions in $x$, what is the value of $a-b$?

A store sells notebooks for $n$ dollars each and pens for $p$ dollars each, where $n$ and $p$ are positive integers. A customer buys $3$ notebooks and $2$ pens for a total of $19$ dollars, and another customer buys $5$ notebooks and $4$ pens for a total of $33$ dollars. Which statement must be true?

A moving company charges a flat booking fee plus a constant rate per hour. For one job, the company charged \260$for$4$hoursofwork.Foranotherjob,thecompanycharged$\$380$ for $7$ hours of work. The company also gives a discount of \15$offthetotalbillforjobsscheduledonweekdays.Ifacustomerschedulesaweekdaymoveandpays$\$445$, how many hours did the move last?

Two linear equations are related by a hidden condition. Equation I is

and Equation II is

where $a$ and $b$ are constants. Given that the ordered pair $(4,2)$ is a solution to both equations, which of the following is an equivalent equation to Equation II after substituting the correct value of $b$ and then multiplying every term by $3$?

A school is planning a rectangular community garden on a coordinate grid. One side of the garden will lie along the line that passes through $(2,1)$ and $(8,13)$. For accessibility, the opposite side must be parallel to this line and pass through the point $(0,5)$. The garden entrance will be placed at the point where this opposite side crosses the $x$-axis. What are the coordinates of the entrance?