Answer:
a) 20
Step-by-step explanation:
If x is the kg of 0.700 grade silver, then:
Silver in ingot + silver in 0.700 alloy = silver in 0.750 alloy
10 + 0.7x = 0.75(x + 12)
10 + 0.7x = 0.75x + 9
1 = 0.05x
x = 20
x>-2
-9x-15<3
•Move the constant to the right
9x<3+15
•calculate
-9x<18
•Divide both sides
x = 5
(7x + 16) = 90 - 39
7x + 16 = 51
7x = 51 - 16 = 35
Answer: 85
Step-by-step explanation: 15 × 6= 90 - 5= 85
