Abcd is a parallelogram. its diagonal, ac, is 18 inches long and forms a 20° angle with the base of the parallelogram. angle abc is 130°. what is the length of the parallelogram’s base, ab?

This is the concept of geometry, to solve for the long base of the parallelogram we use sine rule which states that, given triangle ABC with sides a,b and c
then
a/sin A=b/sin B=c/sin C
From our question, ABC=130, thus b=18 in
BAC=30, the length of the base will be a
thus;
a/sin 30=18/sin 130
a=(18sin 30)/sin 130
a=9/0.7660
a=11.75 inches

The base is therefore 11.75 inches