In a step-deviation table with equal class width $h=10$, the class for which $u_i=0$ is 65-75. Which class carries $u_i=-3$?

$u_i=0$ means $x_i=a$, so a is the class mark of 65-75, $i$.e. $a=70$. Then $u_i=-3$ needs $x_i=a-3h=70-30=40$, which is the class mark of 35-45. "30-40" takes $a=65$, the lower limit, instead of the class mark 70; "45-55" moves only two steps of $h$; "95-105" moves up instead of down (that is $u_i=+3$).