Question

if 10,20,x and 40are In a proportion the value of x

Answer 1

extremes = means
10×40=20×x
x=10×40÷20
x=20

Answer 2

Product of means = Product of extremes
→10/20 = x/40
→10*40 = 20*x
→40 = 20x
→40/20 = x
→x = 2

EmoLord.