"Complementary" angles sum to 90°.
Since we are using minutes as well...
80°+d°+25'+m'=90° subtract 80° from both sides
d°+25'+m'=10° subtract 25' from both sides
d°+m'=9°+60'-25'
d°+m'=9°+35'
9°35'
Answer:

Step-by-step explanation:
So we have the expression:

Distribute the negative:

Combine like terms:

And we're done!