Question

please answer this question
17 , 18, 19

Answer 1

fristly take the mid points of given 2 points and equate it to 20/2 i.e 10

2a–1–3/2 , 7–1/2 =20/2

2a–4/2 = 20/2

2(a–2)/2=10

a–2=10

a=12