Simplify:-5 1/4-(-7 1/2)

D. 2 1/4.

Step-by-step explanation:

First, convert both -5 1/4 and -7 1/2 into improper fraction. These would be -21/4 and -15/2.

-21/4 - (-15/2)

Two negatives in a row make a positive.

-21/4 + 15/2

Double both the numerator and denominator of 15/2 to make it have the same denominator as -21/4. This would 30/4.

-21/4 + 30/4

Put -21 + 30 over 4 to make it a single fraction.

(-21 + 30)/4

Add -21 and 30 to get 9.

9/4

Convert 9/4 into a mixed number: 2 1/4

The answer to -5 1/4 - (-7 1/2) is 2 1/4, which is D.

since the airplane is moving with constant speed then the distance travelled can be calculated by x=u*t

in km/h would be:

x=640*3.5=2.240 km

in m/s would be:

u=640 km/h= 640.000 m/h =640.000/ 3600 m/s =177.8 m/s

t= 3.5 h= 3.5 * 3600 s=12.600 s

then x=u*t= 177.8*12.600= 2.240.280 m