Write an equation to solve these problems

Hi

I have exams in a few weeks and am stuck on some basic questions which the teacher hasn't taught due to their 3 month absence. We didn't finish the syllabus so now I have no notes on this and have no idea (Crying)

I have searched the internet and tried for 2 days, even through some revision guides but I just can't work it out. The answers to some are very easy but the equations I'm perplexed at. I learn through examples and then questioning, not through other methods. If someone can help me with one example, with some general pointers and principles, I'll then try and apply the same principles to the rest to work them out. (this is a mock exam I'm practising at home)

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**Equations and Inequalities**

1. Write down an equation and use it to solve the following problems.

(me: I don't even get if its asking for one equation to solve all the problems or one equation per problem?)

a) Demelza's dad is three time as old as Demelza. The sum of their ages is 52. How old is Demelza?

me: 1/4 x 52 = 13. Demelza is 13 and the dad is 3x13 = 39. 39+13 = 52. Took me about 10s to work out. But I don't even know where to start to put this into an equation.

b) Three consecutive odd numbers add up to 93. Find these numbers.

me: 29+31+33 = 93. Took me less than 7s to work out. I'm clueless about putting it into an equation.

c) Jack and Jill went up the hill to fetch a pail of water. The water weighed 15KG more than the pail. The total weight was 18KG. How heavy was the pail?

me: 18-15 = 3. Pail was 3KG. Is that it? That took less than a second. That seems a bit too simple...

d) Tweedledum and Tweedledee bought a cake and cut it into 3 pieces, one piece for each of them and one piece for Alice. Tweedledum's piece was 50g heavier than Tweedledee's piece. Tweedledee's piece was 30g heavier than Alice's piece. The total mass was 710g. What was the mass of Alice's piece?

me: That took 2 days. I don't know how to start with this honestly like what method to use. I'm missing a systematic approach to all these.

Thank you