Решение:
- а) \( 5x + 12 = 60 + 12 \)
\( 5x + 12 = 72 \)
\( 5x = 72 - 12 \)
\( 5x = 60 \)
\( x = 60 : 5 \)
\( x = 12 \) - б) \( 56 + 8x = 56 + 64 \)
\( 56 + 8x = 120 \)
\( 8x = 120 - 56 \)
\( 8x = 64 \)
\( x = 64 : 8 \)
\( x = 8 \) - в) \( 7x + 88 = 70 + 88 \)
\( 7x + 88 = 158 \)
\( 7x = 158 - 88 \)
\( 7x = 70 \)
\( x = 70 : 7 \)
\( x = 10 \) - г) \( 48 + 13x = 78 + 48 \)
\( 48 + 13x = 126 \)
\( 13x = 126 - 48 \)
\( 13x = 78 \)
\( x = 78 : 13 \)
\( x = 6 \)
Ответ: а) 12; б) 8; в) 10; г) 6.