With all three i need to finish this summer packet quick.

1)
solve for y2

y2 = d + y1

2)
solve for b

b = a - c

3) solve for y1

y1 = y2 - d

Note: you must isolate the variable you are trying to solve for. Do the opposite to both sides because of the equal sign.

1) solve for y₂

d = y₂ - y₁

Isolate y₂. Subtract y₂ from both sdies

d (-y₂) = y₂ (-y₂) - y₁

d - y₂ = - y₁

Divide -1 from both sides to isolate the y₁

(d - y₂)/-1 = (-y₁)/-1

y₁ = (d - y₂)/-1

2) Solve for b

Isolate the b, subtract c from both sides

a = b + c

a (-c) = b + c (-c)

a - c = b

b = a - c 

3) solve for y₁

d = y₂ - y₁

Isolate y₁, subtract y₂ from both sides

d (-y₂) = y₂ (-y₂) - y₁

d - y₂ = - y₁

Divide -1 from both sides.

(d - y₂)/-1 = (-y₁)/-1

y₁ = -d + y₂

hope this helps