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Can you check the following problems, please?

1. If the ratios for microphones to karaoke machines are all equivalent, how can you find the value of x?

table:
microphones 3 9 15 36
karoke 1 3 x 12

Ans: x=5 (because divide each ratio by 3)

2 There are 32 students in Mr. Santana's class, but only 8 computers. What is the ratio of students to computers in simplest form?

Ans: 32:8 = 32/8 = 4students to 1computer

3. Solve for x.
12/20 = x/15

20x=12*15
20x = 180
x = 180/20
x =9

Is there another way to solve the above problem?

4. A Boeing 747 can carry up to 105 tons. What is the maximum weight in pounds if one tone is equivalent to 2000 pounds?

1ton:2000lbs
105tons*(2000lbs/1ton)
210,000 lbs

5.45 is what percent of 90?

45/90 = x/100
90x= 45*100
90x=4500
x=4500/90
x=50%

6. Miss John's favorite animal is the pig. If she collects 13 pig figurines in 4 years, then how many will she collect in 12 years?

13/4yr = x/12yrs
x=3*13 (or 4x=13*12,4x=156,x=156/4,x=39)
x=39 pigs

Thanks