Drop your jaw moderately. Touch the tongue tip behind the bottom front teeth and lift the mid-front part slightly toward the roof.

Americans pronounce mri as ehm-ar-AHY (/ˌɛmɑrˈaɪ/). Stress falls on the third syllable — keep everything else short and quick. You'll hear it in sentences like "The mri scan provided detailed images of the brain".
Record yourself saying "mri" and play it back. The mic stays on your device — nothing's uploaded.
3 syllables, 4 sounds. Tap a syllable to jump to its row, then explore each sound's mouth shape and how it's made.
Open wide for the 'ah' vowel. Lift the tongue back and up while flaring the lips for the 'r'.
The textbook way isn't wrong — it's just not how anyone actually says it.
Stress falls on the third syllable, not the others. Stretch AHY — keep everything else short and quick.
Americans use a relaxed retroflex R — the tongue curls back rather than rolling. The R is one continuous sound with the vowel before it, not two separate sounds.