Stain formed inside the tooth structure from outside sources.

The correct answer is - exogenous stain.

Explanation:

Exogenous stains are the intrinsic stains that affect teeth from inside as stain formed inside due to the external sources. In this type of stain, it formed after a tooth has erupted. These stains can occur when the very inner part known as dentin is turned dark or yellowish.

These stains can not be polished and removed. These can occur if an individual has plaque or calculus in the tooth.

Thus, the correct answer is - exogenous stain.

x = -6.5

explanation:

with this editor, you should be careful to put what you mean. 5/(2x - 7) = 3/(4x +14) is the way i will interpret it. cross multiply

5*(4x + 14) = 3*(2x - 7)       remove the brackets

20x + 70 = 6x - 21             add 21 to both sides

20x+ 70+21= 6x                 combine

20x + 91 = 6x                     subtract 20x

20x-20x+91=6x-20x           combine

91 = - 14x

x = - 91/14

x = - 6.5