Suppose the no. of quarts of egg-shell primer= x
Suppose the no. of quarts of blue base primer= y

Total white colour obtained from egg-shell primer = 70%*x

What we require is value of Y.

We can write this equation down to help us get the desired variables

X*70% + Y*(?? %)= (x+y)* 75%

Statement-1
x+y= 300

Therefore our eqn. becomes X*70% + Y*(?? %)= 300* 75%
But we still have 3 unknowns. Therefore, INSUFFICIENT

Statement-2
Blue base-coat is made up of 90% pure-white colour

Therefore our eqn. becomes X*70% + Y*90%= (x+y)* 75%
We can't really move further. INSUFFICIENT.

Combining 1 & 2, our equation becomes,

X*70% + Y*90%= 300 * 75%= 225

We have x+y=300

Equating both we get X= 225 and Y = 75.

SUFFICIENT.

Answer C?

M2 = 70% pure-white color
M1 = % of Blue base
M = 75% pure-white
N1= pure-white
N2= Blue base

To find: Value of N2

Using Weighted Average:
N1/N2=(M2-M)/(M-M1)

Statement 1:
N1 + N2 = 300
we have no relation between N1 & N2
INSUFFICIENT

Statement 2:
N2 = (0.90) N1
We don't have total of N1 & N2.
INSUFFICIENT

Combining...
N1 + N2 = 300
N2 = (0.90) N1
We can solve to get N1 and N2..
SUFFICIENT

Answer [spoiler]{C}[/spoiler]