Find Angle B in a Quadrilateral with Angles 80°, 95°, and 45°

Question

ABCD is a quadrilateral.

$∢A=80$

$∢C=95$

$∢D=45$

Calculate the size of $∢B$ .

We know that the sum of the angles of a quadrilateral is 360°, that is:

$A+B+C+D=360$

We replace the known data within the following formula:

$80+B+95+45=360$

$B+220=360$

We move the integers to one side, making sure to keep the appropriate sign:

$B=360-220$

$B=140$

140°