Question

1) 3:5 into percentage
2) 7:4 into percentage

Answer 1

1: 60%

"Percent" or "%" means "out of 100" or "per 100", Therefore x% can be written as x100 .
35=x100.
100⋅35=100⋅x100.
3005=100 ⋅x100.
35=60100=60%

2: 175%

Answer 2

1.60%
2.175%
I hope this helps