The average of four numbers is 98. if three of the numbers are 86,87,and 91 what is the fourth number?

To find the average, you have to add all the numbers up and then divide by the amount of numbers you added together.

Equation: (86+87+91+x)/4=98
Solve for x:
86+87+91+x=98*4
264+x=392
x=392-264
x=128

The fourth number is 128

Ithink your answer is b

First locate the turning point (vertex) of the graph. which is at the coordinates x=5 and y=9 or (5; 9).to determine whether it's a maximum or mininum value, you have to discern whether the vertex's y-value is the highest value or lowest value the graph can reach. since the vertex's y-value, 9 is the highest value the graph can reach, it will be a maximum.another basic way to determine whether the vertex's value is max or min is to see if the graph is smiling or sad. if it's smiling, the turning point/vertex would be a minimum, while a sad parabola would have a maximum y-value at the vertex.