In a two-digit number, the units digit is twice the tens digit. If the number is doubled it will be 9 more than the number reversed. Find the number.

T=Tens

U=Unit

From the question... The Unit digit is twice the Tens digit

Let the Number be xy

Meaning

y is the unit number

x is the tenth Number

Can be inferred for the question that

y=2x (i)

Also

If the Number is doubled x2(times 2)

"It'll be 9more than the reversed"

Now listen

if you want to express a 2digit Number...

Let's say 45...

It can be expressed as 10x4 + 5 = 45

or

66 can be expressed as 10x6 + 6 = 66

So

It'd be better if we express this our unknown number like that too

So

Let's express "xy" like "10x + y"

Hope you grab?

Now from the second statement of the question..

If The Number is doubled...It'll be 9 more than the reversed

What is the reverse of that Number??

The reverse would be "10y + x"

You can see that x and y switched places.

so

The statement said...

2(10x + y) + 9 = 10y + x (reversed)

20x + 2y + 9 =10y + x (ii)

Recall from our first eqn

y=2x

Now substitute y=2x into eqn ii

20x + 2(2x) + 9 = 10(2x) + x

20x + 4x +9 = 20x + x

20x - 20x + 4x - x = -9

3x = -9

x=-3

y=2x

y=2(-3)

y=-6

So The Number is 10x + y

= 10(-3) + (-6)

=-30-6

=-36

This answer obeyed the first part of the question because the unit is twice digit(2x3)

Let's check if it obeyed the second part

2[(10(-3) + (-6)] + 9 = 10(-6) + (-3)

2(-30-6) + 9 = -60-3

-63=-63

The 2nd part is also true.

So

Our Number is -36.

I'm Open to corrections if you spot any.

i believe it's a.

i'm not sure on this one, most likely correct.