Lets draw a picture of our problem:
where x denotes the measure of the base angle.
Since interior angles of any triangle add up to 180, we have
[tex]x+3.5x+90=180[/tex]which gives
[tex]4.5x+90=180[/tex]By subtracting 90 to both sides, we have
[tex]\begin{gathered} 4.5x=180-90 \\ 4.5x=90 \end{gathered}[/tex]Finally, by dividing both sides by 4.5, we get
[tex]\begin{gathered} x=\frac{90}{4.5} \\ x=20 \end{gathered}[/tex]Then, the base angle measures 20 degrees and the upper angle measure
[tex]3.5\times20=70[/tex]Therefore, the searched angles measure
[tex]20,70\text{ and 90}[/tex]
