(a) It is given in the question that,

Height of triangle = h

And,

Base of triangle = 15 cm

Area of triangle = 87 cm²

We know that,

Area of triangle = × Base × Height

87 = 1/2 × 15 × h

174 = 15 × h

h =

= 11.6 cm

∴ Height of triangle is 11.6 cm

(b) It is given in the question that,

Height of triangle = 31.4 mm

Base of triangle = b

Area of triangle = 1256 mm²

We know that,

Area of triangle = × Base × Height

1256 = 1/2 × b × 31.4

2512 = b × 31.4

= 80 mm

∴ Base of triangle is 80 mm

(c) It is given in the question that,

Height of triangle = h

Base of triangle = 22 cm

Area of triangle = 170.5 cm²

We know that,

Area of triangle = × Base × Height

170.5 = × 22 × h

341 = 22 × h

h = 341/22

= 15.5 cm

∴ Height of triangle is 15.5 cm