4. Find the mistake and correct, 10x+7y=-
- 7x-2y-1
STEP 41 2 (lóx+ 7y=-1)
77-4x-2y=-1)
STEP #2 20x+144 = - 22
-498-my
- 29x = -23
-29
-29
X
23 름 or x = 0.99
10 (0.79) + 7y=-11
7.9+7y=-
STEP 3:
-7.9
+y=-11.9
+
y=-1.7
(0.79,-17)
STEP 4:
a) At what step did the make mistake occur?
b) Describe the mistake.

51

step-by-step explanation:

73-22=51 the   mass number minus the amount of protons gives you the amount of neutrons

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

shorter then the tree