4a I do not understand the process

9/40

Step-by-step explanation:

He needs 5/8, he already has 2/5, so still needed is 5/8-2/5.

To add or subtract fractions, the denominators must be equal.

Simplest approach is to multiply them. 8 times 5 is 40, so 40 is the new denominator we need for both fractions.

So first we convert 5/8 to 25/40.

Then we convert 2/5 to 16/40.

Now we can subtract them:

25/40 - 16/40 = 9/40.

9/40 cannot be simplified so this is the final answer.

There are some basic rules you need to know to work with fractions. If above work is too fast, comment below for deeper explanation.

3-4

step-by-step explanation:

the answer is 3-4 because both 45 and 60 has a multiple of 15.

45/3=15

60/4=15

therefore the odds against selecting a red is 4-3

a 4/6 = 9/12   not proportional

step-by-step explanation:

to find which are not proportional, we can use cross products

if it is true, they are proportional.   if it is not true, they are not proportional.

a 4/6 = 9/12

4* 12 = 6*9

48 = 54

not this is not proportional  

b 2/3 = 12/18  

2* 18 = 3 * 12

36 = 36

this is proportional

c 5/4 = 10/8  

5*8 = 4*10

40 = 40

this is proportional

d 7/5 = 35/25

7*25 = 5 * 35

175 = 175

is proportional