So we know the tank already has 5 gallons and we need 9. This means we need 4 more gallons in order to fill up the tank.
If 1/4 gallon is being filled per minute we need to find out how many 1/4 gallons makes up 4 gallons in total.
4 of the 1/4 gallons makes up 1 whole gallon. So since we need 4 whole gallons we would need 16 of the 1/4 gallons.
This means that it will take 16 minutes for the tank to hold 9 gallons of water.
The anwser is 5x-3 because you remove the parentheses and pair like terms
You are given that all three sides are equal. You also know that all three angles are also equal. Therefore since all three angles are equal and every triangle has 180 degrees, each angle is 180/3 = 60
So
7x - 3 = 60 Add three to both sides
7x - 3 + 3 = 60 + 3 Combine
7x = 63 Divide by 7
7x/7 = 63/7
x = 9 And that's your answer.