The trout is swimming 30 ft below sea level,if it were above sea level it would be positive but since its below it is negative. It then swims 20 feet lower so it would be -50 as a short cut you can use in problems like this one is to ignore the sign's and add it regularly then add the sign after the equation is done.
The garden's width is 45. We know this because (length) 35x2 is 70 and you need to neutralize that by taking away 70 from both sides. Now divide by 2 on both sides to neutralize the 2 times x. meaning that leaves us with
