Answer:
The first angle is
.
Explanation:
Let the measure of the second angle be represented by
.
Thus, the first angle =
![(3x+10)^(o)](https://img.qammunity.org/2021/formulas/mathematics/college/uw48ocfphsfie9yczg5bl4xdmhuwkey2xi.png)
Third angle =
![90^(o)](https://img.qammunity.org/2021/formulas/physics/high-school/s31cvz6r6urqaro3oahpsc1h3bqk8u04fq.png)
Sum of angles in a triangle =
![180^(o)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/a5nmxwbaa12c0zlaspgicm36b1es2kj8kl.png)
So that;
+
+ 90 =
![180^(o)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/a5nmxwbaa12c0zlaspgicm36b1es2kj8kl.png)
+
+
=
![180^(o)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/a5nmxwbaa12c0zlaspgicm36b1es2kj8kl.png)
=
-
![100^(o)](https://img.qammunity.org/2021/formulas/mathematics/college/mn815eov8tp7xo4thjvh2sz43a7ptiy6za.png)
=
![80^(o)](https://img.qammunity.org/2021/formulas/mathematics/college/ew0jejlb8yjiarbfshxr31spt3gifqm9yc.png)
divide both sides by 4 to have;
=
![20^(o)](https://img.qammunity.org/2021/formulas/physics/college/eauykj4mna24h1bjqhx2wnyqkkoz0d8igr.png)
The first angle =
![(3x+10)^(o)](https://img.qammunity.org/2021/formulas/mathematics/college/uw48ocfphsfie9yczg5bl4xdmhuwkey2xi.png)
= ( 3 x 20 + 10)
= 60 + 10
=
![70^(o)](https://img.qammunity.org/2021/formulas/mathematics/college/tdllr8aquuybitz3flc4ama4qtph9zeiao.png)
Therefore, the first angle is
.