Question

For every positive 2-digit number, x, with tens digit t and units digit u, let y be the 2-digit number formed by reversing the digits of x. Which of the followingexpressions is equivalent to x − y ?a) 9(t − u) b) 9(u − t) c) 9t − u d) 9u − t e) 0

Answer 1

Answer:

a) 9(t - u)

Step-by-step explanation:

x = 10t + u

y = 10u + t

x - y = 10t + u - 10u - t

= 9t - 9u

= 9(t - u)

Answer 2

The required answer for the question is a) 9(t − u)

What are simultaneous equation?

In mathematics , a set of simultaneous equations, also known as system of equations or an equation system, is a finite set of equations for which common solution are sought.

The given expression of x is given by,

x = 10t + u

If y be the 2-digit number formed by reversing the digits of x

then, the expression for y can be written,

y = 10u + t

Subtracting x with y we obtain,

x - y = 10t + u - 10u - t

Solving them we get

x - y = 9t - 9u

which can be written as,

x - y = 9(t - u)

Hence, the required expressions is equivalent to x − y =  9(t − u)

So the correct answer is a) 9(t − u)

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