I need help working these problems out with showed work pls

1. Complete the calculation with significant figure concerns. PEMDAS (100.4 +9.238 - 10.5) -*3.2 +5.25 x 10 =? 2100.85 2.65 99.14x3.215.25 x103 = 5547.74 5567.34 2.15 2. Rewrite this number into regular notation and round it with 3 sf. 1.3748 x 10-5 D 0.0000137 3. Unit conversion. Convert 12 g/ml into kg/m'. Show key steps in your calculations 17 g/mL = 32 kg/m3 4. There are two stock solutions with the same chemical. One is 100 ml. 0.1 M solution, and the other one is 0.5 M 50 ml. solution. How many mL in maximum you may make a 0.2 M solution by only using these two stock solutions provided? (Water is not available in this question. What you have are those two solutions only) 5. Given a NaOH solution A at room temperature, pH = 9, What is the OH' concentration in this solution A? Take 10 ml of solution A and transfer and mix with 90 ml of water to make solution B. Take 10 mL of solution B and mix with 990 ml water to make solution C. What is the cumulative dilution factor? And what is the pll of solution C? 20 legs 6. There are some rabbits and roosters in a cage. Counting the heads there are 25: counting the legs there are 70. How many roosters and how many rabbits are in that cage OOO OO There are 15 roosters & 10 Tabbits. o o o o o 30 0 0 0 0 0 0 0 40 legs 0 0 0 0 0 7. When you were 3 years old, your elder brother was twice old as you when you are 50 years old, how old will your elder brother be? (u Years 100 years old 0740