So we want to solve like if it was just a basic equation. We start with 25+3.50x<17+7.50x and get rid of our smallest x. That means we get rid of the 3.50x by subtracting from both sides and our new equation is 25<17+4x. Let’s get our x by itself shall we, so let’s subtract 17 from both sides and we get 8<4x. Finally all we do is divide by 4 and just like that 2
Answer:
The inequality that represents the age of the group, "x", is: 
Step-by-step explanation:
To express this problem in an inequality we will attribute the age of the members on the group with the variable "x". There are two available information about "x", the first states that every member of the group is older than 17 years, therefore we can create a inequality based on that:

While the second data from the problem states that none of than is older than 54 years old, this implies that they can be at most that old, therefore the inequality that represents this is:

In order for both to be valid at the same time x must be greater than 17 and less or equal to 54, therefore we finally have:

The value of 3ab+5b-5 is 18
I don't know if my answer is completely correct, but I think it's 100. All triangles add up to 180, and an isosceles triangle has 2 equal sides. 40 would be the 2 sides, and 180 subtracted from 80 equals 100.
4. -8
5. 24
6. I can't see it properly so if it's ÷ answer is 9 if it's - answer is -70