A certain number was increased 5 times, then decreased by 3, then halved. The result was 0.3 less than the original number. What was the original number?

Answer 1

"increased 5 times" could mean

x(+x) 5 times = 6x
or
x*5 = 5x

I'll assume the latter, but you can fix it if you need to

(5x+3)/2 = x - 0.3