Patrick went cycling one weekend.
he cycled 12 fewer kilometres on sunday than he cycled on saturday.
he cycled 38km in total that weekend.
how many kilometres did he cycle on saturday?

For this question, it would be most effective to use an algebraic expression to more easily show what the question is asking. If we use the variable "k" to show the distance in km that he cycled on Sunday, we know that the amount he cycled on Saturday equals k + 12, and the amount that he cycled on the weekend should be the amount of Saturday plus the amount of Sunday. If we write this as an equation we say:
k + k + 12 = 38
=> 2k + 12 = 38
Now we can just rearrange and solve for k:
=> 2k = 26
=> k = 26/2 = 13
Therefore Patrick cycled 13km on Sunday
To solve the answer, we just add 12km to the value for Sunday like so:
12 + 13 = the amount he cycled on Sunday
Hope this helped, remember to please try and understand the maths as well as the answer :))

Element 17 is chlorine it is a group 7 element(halogen) and belongs to period 3 of the periodic table