What is the classification of the triangle by its angle and by its sides?

▪︎In this triangle all angles are less than 90°. We know that angles of a triangle which are less than 90° in measure will be called acute angles. Thus, this triangle is an acute angle when we classify it by it's angles.

▪︎All sides of this triangle are equal. We know that when all sides of a triangle are equal, it is to be called an equilateral triangle. Thus, this triangle is an equilateral triangle when we classify it by it's sides.

Therefore, the correct option is (A) acute, equilateral

the largest number of the four options is 1.8 x 10-2

you have it in scientific notation.

1.80 x 10-6   = 0.00000180

1.80 x 10-4   = 0.000180 (bigger, or "less small", than the former one)

so

1.8 x 10-2       = 0.0180. as you see. the "less small", or the biggest one of them all.

as you have negative exponent, it means you are dividing 1.8 by 100 (i.e. moving the dot towards left, two times).

if you had positive exponent for the scientific notation, power of tenths, you would be multiplying times 100 (moving the dot towards right) as below:

1.8 x (10)2 = 180

so. if you have negative exponent in scientific notation, move the dot toward left. if it is positive, toward right as many times the exponent tells you.