Step-by-step explanation:
a) The dots show 2 angles are the same so therefore the third angle is the same. The multiplier from the small to big triangle is 15÷5=3
Therefore a=3×3=9
b) The dots again show 2 angles are the same so the third must be the same. The multiplier from the small to big triangle is 20÷12=5/3 Therefore
b= 15÷(5/3)=9
c)The dot and the right angle show 2 of the angles are the same meaning the third angle must be the same. The multiplier from small to big triangle is 15÷5=3. Meaning d=4×3=12
