The positions of the digits of a certain two-digit number are swapped. the difference between the original two-digit number and the new two-digit number is 54. the ones digit of the original number is 3 more than twice the tens digit. what is the original two-digit number?

Step-by-step explanation:

let the digit at unit place be x

and digit at ten's place be y

then number=10y+x

when the digits are swapped number=10x+y

also x =2y+3

so 10x+y-(10y+x)=54

10 x+y-10 y-x=54

9x-9y=54

x-y=6

2y+3-y=6

y=3

x=2*3+3=9

number=10×9+3=93

420

Step-by-step explanation:

The number of students in the school is unknown, so we'll call it x.

55% of the number of students are girls.

There are 321 girls.

55% of x = 231

0.55x = 231

x = 231/0.55

x = 420

420