There are a few options we can take. One way is to use the tangent ratio to tie together the opposite and adjacent sides, and then apply the inverse tangent (aka arctangent) to get the angle itself.
Let x be the upper left acute angle, and y be the lower right acute angle.
We can say
tan(angle) = opposite/adjacent
tan(x) = 16/5
x = arctan(16/5)
x = 72.645975 approximately
x = 72.6
and also
tan(angle) = opposite/adjacent
tan(y) = 5/16
y = arctan(5/16)
y = 17.3540246
y = 17.4
Note how x+y = 72.6+17.4 = 90. The two acute angles of any right triangle are complementary, meaning they always add to 90. So if you found x, then you can compute y = 90-x without needing the tangent ratio.
Your calculator needs to be in degree mode when using the arctangent function, which is denoted as [tex]\tan^{-1}[/tex] on many graphing calculators.
