Question 47400
To find the average of a set of numbers (grades), add the numbers and divide by the number of numbers (6 in this case). Amanda's average is 86, so:
{{{84+88+82+90+92+x)/6 = 86}}} simplify and solve for x.
{{{436+x)/6 = 86}}} Multiply both sides of the equation by 6.
{{{436+x = 516}}} Subtract 436 from both sides.
{{{x = 80}}}

The missing grade is 80.