Systems of Linear Inequalities, Word Problems - Examples

Jill is bringing donuts to the office, and bought a combination of plain and frosted donuts. She bought at least twice as many plain donuts as frosted donuts. She also wanted to make sure each of $15$ employees could get at least $2$ frosted donuts (including herself), possibly with leftovers. What is the smallest possible total number of donuts Jill bought?