Here the given expression, 

X2 + X2 is an algebraic expression. Here in this expression the terms are like terms. Now to add them, add their coefficients.

Here in the given expression, the like terms are two X2

Hence, adding their coefficients i.e, 1 + 1 = 2

Therefore, 

X2 + X2 = 2X2.

6% of 350000

$$\begin{gathered} 6100 x 3,50,000 \\ = 6 x 3500 \\ = 21,000. \end{gathered}$$

Hence, 6% of 3,50,000 = 21,000.

The Central Processing Unit, consists of Arithmetic and logic unit and Control unit.

As water is cooled from 4 deg C to 0 deg C, the water reaches its freezing point and starts forming ice crystals. Then the volume of that ice cubes increases and its density decreases. Hence, it is the reason that ice will float on water as ice has less density than the water.

Clove the commonly used spice which is obtained from the flower buds of a tree in the family Myrtaceae, Syzygium aromaticum.

When ice melts it changes its physical state to water. Similarly, when rock melts it changes into lava or magma.

Hence, ice is to water as rock is to lava.