Answer:
80 countries participated in the 1980 olympics in Moscow.
Explanation:
Hello, I think I can help you with this
You can solve this by using a simple rule of three
Step 1
define
140 countries participated in 1984,this was 75% more than the last time,this means that 140 is the 175% of a value that we need to know
if
140 ⇔175%
x? ⇔100%
the relation is

Step 2
solve for x

80 countries participated in the 1980 olympics in Moscow.
Have a nice day