Question

A number consists of two digits. The sum of twice the tens digit an 5 times the units digit is 19. If the digits are reversed, the new number is 54 less than the original number. Find the number

Answer 1

let the number be MN digits,

2M+5N=19
10N+M+54=10M+N

2M+5N=19
9N-9M=-54

check those equations.