Suppose $fis$ a continuous function, and $we$ know the following:

${\displaystyle \underset{2}{\overset{6}{}}}f(x)dx=13$

${\displaystyle \underset{5}{\overset{8}{}}}f(x)dx=15$

${\displaystyle \underset{2}{\overset{8}{}}}f(x)dx=23$

Then,

${\displaystyle \underset{2}{\overset{5}{}}}f(x)dx=$

${\displaystyle \underset{5}{\overset{6}{}}}f(x)dx=$

${\displaystyle \underset{8}{\overset{6}{}}}10f(x)dx=$