A hospital prepares a 100mg supply of technetium-99m which has a half-life of 6 hours.
Write the equation for this situation.
Find the amount of technetium-99m
that remains after 75 hours.

Solve the system of equations. y= 2x y= x^2 - 15

Mr and mrs smith buy tickets for themselves and their four children. the cost of an adult ticket is ? 6 more than the adult ticket. the total cost of the six tickets is ? 40.50 work out the cost of an adult ticket. in your working let c be the cost of the child ticket and a be the cost of the adult ticket.

Adrawer contains 12 identical white socks, 18 identical black socks and 14 identical brown socks. what is the least number of socks you must choose, without looking, to be certain that you have chosen two socks of the same colour?