It looks like you've uploaded a photo with two different questions. Let's go through them step by step:

Question 1 (a):

You have 145 boys and 204 girls who were selected for a volunteer program in Thailand. The goal is to divide the boys and girls into as many groups as possible, where the number of boys and girls in each group is equal.

You have correctly set up the equation to find the total number of people involved in the program: $145 \, \text{boys} + 204 \, \text{girls} = 349 \, \text{people total}.$ Now, the next step would be to divide 349 into as many groups as possible, with the number of boys and girls being the same in each group. The largest number that divides both 145 (boys) and 204 (girls) evenly is the greatest common divisor (GCD).

You’ve written out that: $145 - 1 = 144 \, \text{boys left} \quad \text{and} \quad 144 + 204 = 348.$

So, the total number of people is 348, but you need to find the GCD of 144 and 204, which will give you the size of the groups. Let me calculate that for you.

Question 1 (b):

You are asked how many boys and girls there are in each group. This depends on the largest number of people that can form a group, so finding the GCD is necessary.

Question 2:

You’ve also written about the delivery schedules of three trucks, A, B, and C, which deliver goods to a supermarket every 18, 24, and 36 days, respectively. The question asks how many days it will be before all three trucks deliver goods to the supermarket again.

This involves finding the Least Common Multiple (LCM) of 18, 24, and 36 to determine when they all align.

I can calculate both the GCD for the first problem and the LCM for the second. Would you like me to proceed with those calculations now?