21. In this question the diagrams are not drawn accurately, so the angles cannot be found by measuring with a protractor.
The angles of a triangle add up to 180°.
(a) In this triangle angle A is the same as angle B, and angle C is twice angle B. Work
out each of the three angles.
(b) A factor tree can be used to write a number as the product of prime factors.
So 90 = 2 × 5 × 3 × 3
By drawing a factor tree, or using any other method you know, write as the product
of prime factors.