Respuesta :

AmazingMc
15+17+28+30=90, if theres another number than there r 5 total numbers, 23*5=115, 115-90=25, so 25
apologiabiology
mean is add the numbers and divide the result by how many numbers there are
mean=23
1 missing number which is x
5 numbers including missing one 
(15+17+28+30+x)/5=23
solve for x
multiply both sides by 5
15+17+28+30+x=115
add like terms
90+x=115
subtract 90
x=25

the missing number is 25