Step-by-step explanation: Using the equation, y = mx + b, the slope-intercept form, plug in the values you have and solve for b. (m is the slope.) You have y = -8 and x = 4 and m = 1/2.
Since d is being subtracted from bc, we first add d to each side. Now we are left with a + d = bc.
Since b is being multiplied by c to be bc, we divide both sides by c.
We now have a/c + d = b
Your solution is: b = a/c + d
In step 3, you added 8x onto the other side instead of subtracting it from 15x.
Since 1sand=3.5compost you can set up the ratio 1/3.5 or 1 sand for every 3.5 compost. If you change the number of sand to three, then you multiply the top by three since 1*3=3. To keep the mixed number equal you would have to multiply the bottom number by three as well. This means that you can multiple all the sand by 3.5 to get how much compost is needed.