In $\Delta XYZ$,$\angle X : \angle Y : \angle Z = 1 : 4 : 4$,then $\angle Z = \ldots$ (in $^{\circ}$)

If the measure of an acute angle is $x^{\circ}$,find the difference of the measure of its supplementary angle and complementary angle. (in $^{\circ}$)

In $\Delta ABC$,$\angle B = \frac{\angle A + \angle C}{2}$ and $\angle A : \angle C = 1 : 2$. Find the measure of each angle of $\Delta ABC$.

In the following figure,lines $AB$ and $CD$ intersect at $O.$ If $\angle AOC + \angle BOE = 100^{\circ}$ and $\angle BOD = 40^{\circ},$ find $\angle BOE$ and reflex $\angle COE.$

If one of the two angles of a linear pair has measure $75^{\circ}$,the measure of the other is $\ldots \ldots \ldots$ (in $^{\circ}$)

Can a triangle have all angles less than $60^{\circ}$? Give reason for your answer.