A student prepared a stock solution by dissolving 20.0 g of NaOH in enough water to make 150 mL of solution. She then took 15.0 mL of the stock solution and diluted it
with enough water to make 65.0 mL of a final solution. What is the concentration of NaOH for the final solution?
0.769 M
O 0.548 M
1.82 M
1.40 M

i do not get it   at all

the answer is d. 74.02

percent abundance for cu-63 can be shown as:

63 x + 65 (1-x) = 62.9296

65 - 62.9296 = 2 x

x = 1.035

thus, percent abundance for cu-63 is 1.035

percent abundance for cu-65 can be shown as:

63 x + 65 (1-x) = 64.9278

65 - 64.9278 = 2 x

x = 0.0361

thus, percent abundance for cu-63 is 0.0361

the mass spectrum of cu-63 showing the intense peak as, this isotope is found in nature more abundantly around 92.38 % in comparison to cu-65 which is found 62.58 % naturally

the correct answer would be b) volume versus temperature, because they are also directly proportional.