Open the image in Paint (If you have Windows) and save them as a [.png] That should reduce the file size.
Hmm... IME, png files are bigger than jpg, all else being equal.
There are many, many tricks to deal with too-large files. One of my personal favorite workarounds* is to copy the image and paste into PowerPoint. Then use "Save as Picture" in PPT to save the image as a jpg. Sometimes, the act of pasting it into PPT and then copying it again will make the image size (file size, so to speak) substantially smaller. The image can also be resized in PPT -- or the original file can be resized (e.g., if one lives in the Wintel world) -- using the options Windows provides when right clicking on a displayed graphic file such as a jpg. See Win10 screenshot below.
Speaking of
screenshots -- that's always an option, too
So many workarounds*, so little time...
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* re: workarounds
xkcd.com