2/5 - 4/5 + -9/10 =

, will mark brainliest for answer with an explanation

Step-by-step explanation:

-2/5 - 4/5 + -9/10

= -2/5 - 4/5 - 9/10

= {-2(2) -4(2) - 9)/10

= (-4 - 8 - 9)/10

= -21/10

= -2 1/10

answer:  

step-by-step explanation:

here x represents the height of the pole,

and, the height of the shadow of the pole is 12 feet.

also, the angle of elevation from the top of the pole is 40°,

therefore,

by the low of sine,

which is the required equation for finding the value of x,

sounds & other waves originate from any vibrating object