Let c = grams of copper to be added
(grams of silver) / (grams of copper and silver) < = .90
387+%2F+%28c+%2B+387%29+%3C=+.9
387+%3C=+.9%28c+%2B+387%29
387+%3C=+.9c+%2B+348.3
.9c+%3E=+387+-+348.3
.9c+%3E=+38.7
c+%3E=+43g
At least 43 grams of copper must be added
check:
387+%2F+%28c+%2B+387%29+%3C=+.9
387+%2F+%2843+%2B+387%29+%3C=+.9
387+%2F+430+%3C=+.9
.9+%3C=+.9
Uhhhhh kid idol step by step uhhhhhhhhhgh
Equation changes to 4x+(8 x .8)= 40. changes to 4x+6.4=40. subtract 6.4 from fourty, and you get 33.6. then you divide 33.6 by 4 and you get 8.4
x=4
2016 is least common factor