45:10 I think ? .. that’s how my teacher did it
Answer:
x=73
Step-by-step explanation:
18 kg of 15% copper and 72 kg of 60% copper should be combined by the metalworker to create 90 kg of 51% copper alloy.
<u>Step-by-step explanation:</u>
Let x = kg of 15% copper alloy
Let y = kg of 60% copper alloy
Since we need to create 90 kg of alloy we know:
x + y = 90
51% of 90 kg = 45.9 kg of copper
So we're interested in creating 45.9 kg of copper
We need some amount of 15% copper and some amount of 60% copper to create 45.9 kg of copper:
0.15x + 0.60y = 45.9
but
x + y = 90
x= 90 - y
substituting that value in for x
0.15(90 - y) + 0.60y = 45.9
13.5 - 0.15y + 0.60y = 45.9
0.45y = 32.4
y = 72
Substituting this y value to solve for x gives:
x + y = 90
x= 90-72
x=18
Therefore, in order to create 90kg of 51% alloy, we'd need 18 kg of 15% copper and 72 kg of 60% copper.
Answer:
= -4x + 7 is the correct answer
Step-by-step explanation:
Answer:
B :step 2 she didnt collect all the like terms and calculate
Step-by-step explanation:
first rewrite remove all ( )Parentheses
2nd collect all like terms and calculate
a^4 + 7a -16 -12^a^3 + 5a -3
a^4 + 12a - 19 - 12a^3 ( Like terms are 7a +5a and -16 +-3)
so she skipped the second step
