Question

Somebody help. I can’t figure this question out. thanks

Answer 1

$21 \div 30 = 14 \div 14 + x$
$30 \times 14 = 420$
$21 \times 14 + x = 294 + 21x$
$420 = 294 + 21x$
$420 - 294 = 126$
$126 = 21x$
$126 \div 21 = 6$
$x = 6$

Answer 2

The large triangle and the smaller one are similar. Comparing long sides to short ones, we get
.. (30 mm)/(21 mm) = (14 mm +x)/(14 mm)
.. (14 mm)*10/7 = 14 mm +x
.. (14 mm)*(10/7 -1) = x
.. (14 mm)*(3/7) = x = 6 mm

The value of x is 6 mm.