The two triangles are congruent. We can prove this using SSS. The upper triangle is a mirrored copy of the lower triangle.
Since angle1 = 160 degrees, this means angle2 = 160 also. This is because the corresponding pieces of congruent triangles match up. Or you could use the second part of the hint which says "Opposite angles in a rhombus are congruent".
Let x be the measure of angle 3. For either isosceles triangle, it has congruent base angles measured x degrees. They add to the 160 degrees mentioned earlier to get a total of 180.
