Given interchanges : 

Signs + and - , numbers 4 and 8.

In an algebraic expression, like terms are terms that contain the same variables raised to the same powers. Calculating x-squared plus x-squared is a matter of combining like terms. 

Now x^2 + x^2 = 2x^2

Hence, x-squared plus x-squared is equal to 2 times x squared.

Given 7 + 7/7 + 7 x 7 - 7

By using BODMAS rule,

7 + 1 + 7 x 7 - 7

= 8 + 49 - 7

= 57 - 7

= 50.

Hence 7 + 7/7 + 7 x 7 - 7 = 50.

This can be done in a method called Approximation.

Now, 

$$\begin{gathered} 52 + 63 + 6 + 72 = ? x 3.34 \\ 25 + 216 + 6 + 49 = ? x 3.34 \\ 296 = ? x 3.34 \\ ? = 2963.34 = 88.622 ≅ 89 \end{gathered}$$

$$\begin{gathered} 7 + 7 ÷ 7 + 7 x 7 + 7 - 7 ÷ 7 + 7 x 7 \\ = 7 + 1 + 49 + 7 - 1 + 49 \\ = 8 + 56 + 48 \\ = 56 + 56 \\ = 112 \end{gathered}$$

Unit digit of this expression is always 1 as the base ends with 1. 

For the tenth place digit we need to multiply the digit in the tenth place of the base and unit digit of the power and take its unit digit.

i.e, tenth place digit in 2151 is 5 and

tenth place digit in power 415 is 1

And the units digit in the product of 5 x 1 = 5

Therefore, last two digits of 2151415 is 51.

Given equation is  

  192.5 ×19p = 197   

Here it is in the form of am × an = am+n  

 Here m = 2.5 , n = p, m+n = 7

 => 2.5 + p = 7 

 => p = 7 - 2.5

 => p = 4.5

Using Trial and error method,

From the options  u = 1, v = 3/2 satisfies both the equations.

Given (49.001)²  = ?

=> =~ 49 x 49

=~ 2401

=~ 2400