Please answer correctly !!!!!!! Will mark brainliest !!!!!!!!!!!

Answer:
100
Step-by-step explanation:
perfect square (a - b)^2 = a^2 - 2ab + b^2
In this case
20x = 2 * x * 10
and
10^2 = 100
so
(x - 10)^2 = x^2 - 20x + 100
Therefore, the missing constant term is 100
.