In a certain code language, 'FAITH' is written as 'JDMWL', and 'GLASS' is written as 'KOEVW'. How will 'HEART' be written in that language?

Let's find the character shifting rules for each letter positional pair:
FAITH → JDMWL

F (6) $+4=$ J (10)

A (1) $+3=$ D (4)

I (9) $+4=$ M (13)

T (20) $+3=$ W (23)
Testbook

H (8) $+4=$ L (12)

Pattern: Alternating shifts of +4,+3,+4,+3,+4.

GLASS → KOEVW

G (7) $+4=$ K (11)

L (12) $+3=$ O (15)

A (1) $+4=$ E (5)

S (19) $+3=$ V (22)

S (19) $+4=$ W (23)

This perfectly confirms the alternating +4,+3 shift pattern.

Now apply it to HEART:

H (8) $+4=$ L (12)

E (5) $+3=$ H (8)

A (1) $+4=$ E (5)

R (18) $+3=$ U (21)

T (20) $+4=$ X (24)

Combining these letters yields LHFUX.