I need help with questions 3 and 5, i've been struggling for ages but i'm baffled! Someone help please. :)

3. 2x + y = 21.

Step-by-step explanation:

3. The diagonals of a rhombus  are perpendicular and bisect each other.

So the slope of line AC  = -1/m

= -1 / 1/2 = -2.

AC has coordinates (5, 11) so using the point-slope form of a line:

y - 11 = -2(x - 5)

y = -2x + 10 + 11

2x + y = 21.

5.   Line L:

x + 2y = 12

2y = -x + 12

y = -1/2x + 6

The slope is -1/2 so the slope m of M is -1 / -1/2 = 2.

4

step-by-step explanation:

6 (donuts) divided by 3 is 2.

so 2/3 means 2 times 2, which is 4/6.

you get two and your friend gets four.

step-by-step explanation:

what grade level is this? need to know so i can look in my old textbooks!