Solving systems of equations using substitution x=3y+10. x=y+2

Prove that quadrilateral is a rhombus.

The ratio of the measures of the three angles in a triangle is 2: 9: 4. find the measures of the angels

Solve: 25 points find the fifth term of an increasing geometric progression if the first term is equal to 7−3 √5 and each term (starting with the second) is equal to the difference of the term following it and the term preceding it.