ANSWER
The smaller angle is
[tex]y = 36 \degree[/tex]
.EXPLANATION
Let the angles be
[tex]x \: and \: \: y[/tex]
where y is the smaller angle.
Since they are supplementary, they will add up to 180°.
This implies that,
[tex]x + y = 180 \degree...(1)[/tex]
If one angle is 4 times the other, we can then write the following equation,
[tex]x = 4y...(2)[/tex]
We put equation (2) into equation (1) to get,
[tex]4y + y = 180 \degree[/tex]
[tex]5y = 180 \degree[/tex]
We divide through by 5 to obtain,
[tex]y = 36 \degree[/tex]
This implies that,
[tex]x = 4(36)[/tex]
[tex]x = 144 \degree[/tex]