A+b+c=68
a-b=5
b:c=3

a, b,c=?

a = 32

b= 27

c = 9

Step-by-step explanation:

a= 5+ b from the second equation

c= b/3 from the third equation

substitute the above equations to the first equation then solve for b your answer will be 27

substitute the value of b in the second equation you will solve for a

perform the same substitution to the third equation you will get the answer for c

Step-by-step explanation:

a-b=5<=>a=5+b (1)

b:c=3<=>b=3c (2)

a+b+c=68<=>5+b+3c+c=68<=>5+3c+3c+c=68

<=>7c=63<=>c=9

Fill in (2), we have b=3c=3.9=27

and in (1), we have a=5+b=5+27=32

So, a=32, b=27, c=9

the value of v.w= -12.

step-by-step explanation:

we are given three vector r,v and w as:

r = < 5, -5, -2> ; v = < 2, -8, -8> ; w = < -2, 6, -5>

we know that r,v and w could also be represented as:

r=5i-5j-2k

v=2i-8j-8k

and w= -2i+6j-5k

where i,j and k are the unit vectors of x,y and z-axis respectively.

also we know that it has the following property:

i.i=1 ; j.j=1; k.k=1

and i.=j.i=i.k=k.i=j.k=k.j=0

i.e. when we multiply two vectors or we find it's dot product we need to only multiply the components of x coordinates with each other; y with each other and z with each other.

hence, v.w= (2i-8j- -2i+6j-5k)

                  = 2×(-2)+(-8)×(6)+(-8)×(-5)

                  = -4-48+40

                  = -12

hence, v.w= -12