Answer:
-1.2
Step-by-step explanation:

Subtract 3.9 from -9.18 to isolate the variable.

Divide -13.08 by 10.9

Which equals

Answer:
x=26
Step-by-step explanation:
3x +12 =90
subtract 12 from each side
3x=78
divide 3 from each side
x=26
The topics you should learn are equating denominators and fractions. This is summing up simple fractions.
So we have to make denominators' numbers the same in order to sum up them all (we can sum fractions if the denominators are the same) , and we did it by cross product (that thing on the picture)
Equating by lcm (least common multiple) is the easiest way, because you might see bigger numbers on other questions, and cross product will bring much bigger numbers, so this technic might confuse you.
By the way lcm of 4 and 5 is already 20
Hope it helps!
It’s B
Explanation: use desmos or trust me lol
6x^2 is the answer. thanks for asking it.