There’s an app called Photomath download its free it’s simple it gives u the answer and shows how to work it out
Answer:
you add them, but keep the sign
Step-by-step explanation:
Given:


To find:
The obtuse angle between the given pair of straight lines.
Solution:
The slope intercept form of a line is
...(i)
where, m is slope and b is y-intercept.
The given equations are


On comparing these equations with (i), we get


Angle between two lines whose slopes are
is

Putting
and
, we get



Now,
and 
and 
and 
, so it is an obtuse angle and
, so it is an acute angle.
Therefore, the obtuse angle between the given pair of straight lines is 120°.
Answer:
9/10
Step-by-step explanation:
7
+
2
= 9
10 and 10 are equal so they stay the same.