Question 1162558
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Answer: 
<font color=red>80 kilograms</font> of the 30% fat content chocolate
<font color=red>20 kilograms</font> of the 60% fat content chocolate


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Work Shown:


We have two kinds of chocolate, which we'll call A and B
x = amount of chocolate A
y = amount of chocolate B
amounts are in kilograms
x+y = total amount of chocolate from both candies
x+y = 100, since we want 100 kg total
y = -x+100, solve for y


0.30x = amount of pure fat from chocolate A
0.60y = amount of pure fat from chocolate B
0.30x+0.60y = total amount of pure fat from both chocolates combined
0.30x+0.60y = 0.36*100
0.30x+0.60y = 36
the expression 0.36*100 represents 36% of the total amount 100 kg is pure fat. So we have 36 kg of pure fat


Plug in y = -x+100. Solve for x.
0.30x+0.60y = 36
0.30x+0.60( y ) = 36
0.30x+0.60( -x+100 ) = 36 ... replace y with -x+100
0.30x-0.60x+60 = 36 ... distribute
-0.30x+60 = 36
-0.30x = 36-60
-0.30x = -24
x = -24/(-0.30)
x = 80


We can now find the value of y with this x value
y = -x+100
y = -80+100
y = 20
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