Question 648088
To find the average of a set of numbers is, as you know,the sum of the numbers divided by the number of numbers, so, if you have 3, x, 6, and 12 whose average is at least 12, then...
{{{(3+x+6+12)/4 >= 12}}} Simplify.
{{{(21+x)/4 >= 12}}} Multiply both sides by 4.
{{{21+x >= 48}}} Now subtract 21 from both sides.
{{{x >= 27}}}
x is at least 27