40x - 24 - 33x - 77 = 102
40x - 33x = 102 + 24 + 77
7x = 203
x = 29
Usually when you do expressions involving subtraction you can do Keep, Change ,Change
That means you keep the sign of the first number and change the other two signs.
It is best you rewrite the expression to addition because a lot of people don't do well with subtracting .
-2-3x=3+1x
-2-3=1x+3x
-5=4x
x=-1.25
431.2+826.4d=2910.4
431.2 is only the first day therefore it doesn't need the variable because the variable represents the number of days. 826.4 even says "each remaining day" referring to what the variable represents.
